Results for “fractional dosing”
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Dose Optimization Trials Enable Fractional Dosing of Scarce Drugs

During the pandemic, when vaccines doses were scarce, I argued for fractional dosing to speed vaccination and maximize social benefits. But what dose? In my latest paper, just published in PNAS, with Phillip Boonstra and Garth Strohbehn, I look at optimal trial design when you want to quickly discover a fractional dose with good properties while not endangering patients in the trial.

[D]ose fractionation, rations the amount of a divisible scarce resource that is allocated to each individual recipient [36]. Fractionation is a utilitarian attempt to produce “the greatest good for the greatest number” by increasing the number of recipients who can gain access to a scarce resource by reducing the amount that each person receives, acknowledging that individuals who receive lower doses may be worse off than they would be had they received the “full” dose. If, for example, an effective intervention is so scarce that the vast majority of the population lacks access, then halving the dose in order to double the number of treated individuals can be socially valuable, provided the effectiveness of the treatment falls by less than half. For variable motivations, vaccine dose fractionation has previously been explored in diverse contexts, including Yellow Fever, tuberculosis, influenza, and, most recently, monkeypox [712]. Modeling studies strongly suggest that vaccine dose fractionation strategies, had they been implemented, would have meaningfully reduced COVID-19 infections and deaths [13], and perhaps limited the emergence of downstream SARS-CoV-2 variants [6].

…Confident employment of fractionation requires knowledge of a drug’s dose-response relationship [613], but direct observation of both that relationship and MDSE, rather than pharmacokinetic modeling, appears necessary for regulatory and public health authorities to adopt fractionation [1516]. Oftentimes, however, early-phase trials of a drug develop only coarse and limited dose-response information, either intentionally or unintentionally. A speed-focused approach to drug development, which is common for at least two reasons, tends to preclude dose-response studies. The first reason is a strong financial incentive to be “first to market.” The majority of marketed cancer drugs, for example, have never been subjected to randomized, dose-ranging studies [1718]. The absence of dose optimization may raise patients’ risk. Further, in an industry sponsored study, there is a clear incentive to test the maximum tolerated dose (MTD) in order to observe a treatment effect, if one exists. The second reason, observed during the COVID-19 pandemic, is a focus on speed for public health. Due to ethical and logistical challenges, previously developed methods to estimate dose-response and MDSE have not routinely been pursued during COVID-19 [19]. The primary motivation of COVID-19 clinical trial infrastructure has been to identify any drug with any efficacy rather than maximize the benefits that can be generated from each individual drug [3182021]. Conditional upon a therapy already having demonstrated efficacy, there is limited desire on the part of firms, funders, or participants to possibly be exposed to suboptimal dosages of an efficacious drug, even if the lower dose meaningfully reduced risk or extended benefits [16]. Taken together, then, post-marketing dose optimization is a commonly encountered, high-stakes problem–the best approach for which is unknown.

…With that motivation, we present in this manuscript the development an efficient trial design and treatment arm allocation strategy that quickly de-escalates the dose of a drug that is known to be efficacious to a dose that more efficiently expands societal benefits.

The basic idea is to begin near the known efficacious dose level and then deescalate dose levels but what is the best de-escalation strategy given that we want to quickly find an optimal dosage level but also don’t want to go so low that we endanger patients? Based on Bayesian trials under a variety of plausible conditions we conclude that the best strategy is Targeted Randomization (TR). At each stage, TR identifies the dose-level most likely to be optimal but randomizes the next subject(s) to either it or one of the two dose-levels immediately below it. The probability of randomization across three dose-levels explored in TR is proportional to the posterior probability that each is optimal. This strategy balances speed of optimization while reducing danger to patients.

Read the whole thing.

Fractional Dosing Trials

My paper Testing fractional doses of COVID-19 Vaccines, co-authored with Kremer et al., has now been published at PNAS. I covered the paper in A Half Dose of Moderna is More Effective than A Full Dose of Astra Zeneca and other posts so I won’t belabor the basic ideas. One new point is that thanks to the indefatigable Michael Kremer and the brilliant Witold Wiecek, clinical trials on fractional dosing on a large scale have begun in Nigeria. Here are a few key points:

WHO SAGE Outreach: The authors have met and presented their work to the World Health Organization (WHO) Strategic Advisory Group of Experts on Immunization (SAGE), with follow-up meetings to present evidence coming from new studies.

DIL Workshop and Updates: In the fall of 2021, the Development Innovation Lab (DIL) at UChicago, led by Professor Kremer, hosted a workshop on fractional dosing, collecting updates from clinical researchers from multiple countries conducting fractional dosing trials for COVID-19 vaccines. The workshop also covered issues relating to trial design and included participants from Belgium, Brazil, Ghana, the Netherlands, Nigeria, Thailand, South Africa, UK and the US. 

CEPI Outreach: Professor Kremer has also presented this research to The Coalition for Epidemic Preparedness Innovations (CEPI), which is now pursuing a platform trial of fractional dosing.

Country Trials – Nigeria: With the support of DIL and the research team and generous support and advice from WAM Foundation, the charitable arm of Weiss Asset Management and Open Philanthropy, a trial is being conducted in Nigeria by the Nigerian Institute of Medical Research, National Institute of Pharmaceutical Research and Development, National Agency for Food and Drug Administration and Control, and the National Primary Health Care Development Agency, in coordination with the Federal Ministry of Health.

A comprehensive list of all the trials on fractional dosing conducted to date is at the link. Fractional dosing may come too late for COVID-19 vaccines but perhaps next time a shortage of a vaccine looms we will be more quick to consider policies to stretch supplies.

Thailand and The WHO on Fractional Dosing

Thailand will study fractional dosing:

Thailand is studying the possibility of injecting coronavirus vaccines under the skin to try to stretch its limited supply, a health official said on Thursday, as the country races to inoculate the public faster amid a worsening epidemic.

“Our previous experience shows that intradermal injections uses 25% of a muscular injection, but triggers the same level of immunity,” head of the medical science department, Supakit Sirilak told reporters.

I am also pleased that the WHO’s SAGE has issued an interim statement on fractional doses:

WHO, with support of the Strategic Advisory Group of Experts (SAGE) on Immunization and its COVID-19 Vaccines Working Group, is reviewing the role of fractionating doses as a dose-sparing strategy in light of global vaccine supply constraints. SAGE is continuously reviewing the literature and has reached out to vaccine manufacturers and the research community for available information.

….While SAGE acknowledges the potential public health benefits of dose-sparing strategies to increase vaccine supply and accelerate population-level vaccination coverage, and possibly also a reduction in reactogenicity, SAGE considers there is currently insufficient evidence to recommend the use of fractional doses. Any use of a fractional dose at this point in time constitutes an off-label use of the vaccine. SAGE encourages research in the area, with a particular emphasis on research into using fractionated doses as potential boosters and fractional doses in children and adolescents.  Programmatic and operational considerations should be considered from the start.

The statement is reasonable but could have used some cost-benefit analysis. Given shortages, I’d push for a challenge trial or some field trials. I agree that if we are to have boosters and to vaccinate young children we should be looking very hard at fractional doses as they are likely to be sufficient for purpose and to preserve as much supply as possible for the rest of the world.

By the way, I think you can also see some status quo bias in the WHOs position on boosters: they are not (yet) enthusiastic about increasing supply with fractional doses but they are very negative about reducing supply with boosters. What a miracle that the status quo is just right!

In the context of ongoing global vaccine supply constraints, administration of booster doses will exacerbate inequities by driving up demand and consuming scarce supply while priority populations in some countries, or subnational settings, have not yet received a primary vaccination series.

The WHO also doesn’t note that if developed countries go for boosters then the case for fractional doses elsewhere to make use of the even more limited supply is likely even stronger.

Here’s my paper with co-authors on fractional doses.

Hat tip: Witold.

Use Fractional Dosing to Speed Vaccination and Save Lives

I’ve been shouting about fractional dosing since January, most recently with my post A Half Dose of Moderna is More Effective Than a Full Dose of AstraZeneca and the associated paper with Michael Kremer and co-authors. Yesterday we saw some big movement. Writing in Nature Medicine, WHO epidemiologists Benjamin Cowling and Wey Wen Lim and evolutionary biologist Sarah Cobey title a correspondence:

Fractionation of COVID-19 vaccine doses could extend limited supplies and reduce mortality.

Exactly so. They write:

Dose-finding studies indicate that fractional doses of mRNA vaccines could still elicit a robust immune response to COVID-192,3. In a non-randomized open-label phase 1/2 trial of the BNT162b2 vaccine, doses as low as one third (10 μg) of the full dose produced antibody and cellular immune responses comparable to those achieved with the full dose of 30 μg (ref. 4). Specifically, the geometric mean titer of neutralizing antibodies 21 days after the second vaccine dose was 166 for the group that received 10 μg, almost the same as the geometric mean titer of 161 for the group that received 30 μg, and 63 days after the second dose, these titers were 181 and 133, respectively4. For the mRNA-1273 vaccine, a dose of 25 μg conferred geometric mean PRNT80 titers (the inverse of the concentration of serum needed to reduce the number of plaques by 80% in a plaque reduction neutralization test) of 340 at 14 days after the second dose, compared with a value of 654 for the group that received the standard dose of 100 μg (ref. 5). According to the model proposed by Khoury et al.6, if vaccine efficacy at the full dose is 95%, a reduction in dose that led to as much as a halving in the post-vaccination geometric mean titer could still be in the range of 85–90%. Although other components of the immune response may also contribute to efficacy, these dose-finding data are at least indicative of the potential for further exploration of fractionation as a dose-sparing strategy. Durability of responses after fractional doses should also be explored.

…Concerns about the evolution of vaccine resistance have been posited as a potential drawback of dose-sparing strategies. However, vaccines that provide protection against clinical disease seem to also reduce transmission, which indicates that expanding partial vaccination coverage could reduce the incidence of infection. As described in a recent paper, lower prevalence should slow, not accelerate, the emergence and spread of new SARS-CoV-2 variants8.

…In conclusion, fractionated doses could provide a feasible solution that extends limited supplies of vaccines against COVID-19, which is a major challenge for low- and middle-income countries.

Also a new paper in preprint just showed that 1/4 doses of Moderna create a substantial and lasting immune response on par with that from natural infection.

Here we examined vaccine-specific CD4+ T cell, CD8+ T cell, binding antibody, and neutralizing antibody responses to the 25 ug Moderna mRNA-1273 vaccine over 7 months post-immunization, including multiple age groups, with a particular interest in assessing whether pre-existing crossreactive T cell memory impacts vaccine-generated immunity. Low dose (25 ug) mRNA-1273 elicited durable Spike binding antibodies comparable to that of convalescent COVID-19 cases. Vaccine-generated Spike memory CD4+ T cells 6 months post-boost were comparable in quantity and quality to COVID-19 cases, including the presence of TFH cells and IFNg-expressing cells.

Finally, an article in Reuters notes that Moderna are preparing to launch a 50 ug dose regimen as a booster and for children. Thus, contrary to some critics of our paper, the technology is ready.

Frankly, governments are way behind on this–they should have been pushing the vaccine manufacturers and funding trials on alternative dosing since at least January. Indeed, imagine how many lives we might have saved had we listened to Operation Warp Speed advisor Moncef Slaoui who advocated for half doses in January. On a world scale, we could have vaccinated tens even hundreds of millions more people by now had we ramped up fractional dosing.

At this point, it’s my view that there is enough knowledge to justify rolling out alternative dosing in any hot spot or in any country worried about outbreaks. Roll it out in a randomized fashion (as Kominers and I discussed in the context of the US vaccination rollout) to study it in real time but start the roll out now. Lives can be saved if we speed up vaccination, especially of the best vaccines we have, the mRNAs. Moderna and Pfizer have together pledged to deliver (mostly Pfizer and mostly through the US) some 250m vaccine doses to COVAX in 2021 for delivery to less developed countries. If we go to half-doses that becomes 500m doses–a life saver. And recall these points made earlier:

Judging by neutralizing antibodies, a 50 ug dose of, for example, Moderna looks to be more effective than standard dosing of many other vaccines including AZ and J&J and much better than others such as Sinovac. Thus alternative dosing is a way to *increase* the quality of vaccine for many people.

A 50 ug dose vaccine available today is much higher quality than a 100 ug dose vaccine available one year from now.

If we have the will, we can increase vaccine supply very rapidly.

Fractional Dosing Study in Brazil

Fiocruz, the Brazilian public health institute, will test half doses of the AstraZeneca vaccine. Not much information available yet. From a Google Translate article.

BANDNews: Fiocruz, in partnership with the government of Espírito Santo, is going to carry out a study with the application of half a dose of the Astrazeneca vaccine to the entire population of the municipality of Viana, in Greater Vitória.

The city has about 35 thousand inhabitants.

The immunization will take place on Sunday, June 13, and residents will be able to choose whether they want to participate in the study.

According to the state secretary of Health, Nésio Fernandes, there is already evidence of the effectiveness of the application of half a dose of the vaccine in immunization against Covid-19.

If the experience is successful, it will be possible to double the number of people vaccinated in the country with the immunizing agent produced by Fiocruz.

See my previous posts on fractional dosing for why this is very important.

Hat tip: Cisco Costa.

Fractional Dosing Trials Now!

Fractional dosing has the potential to massively increase the supply of COVID vaccine. The Moderna Phase I clinical trial and Pfizer Phase I/II trials already indicated a substantial immune response with smaller doses but the vaccine companies are under-incentivized to run additional fractional dosing trials (they won’t gain trillions, at best they will gains billions and might even lose some profit) and governments and private organizations are not picking up the ball. There are just two small trials underway that I am aware of:

N.B. now that we know that the vaccines work. we don’t need to study every dosage for efficacy against the virus. Instead of efficacy studies we can study how the vaccine is working in the body compared to those fully immunized, immunogencity trials (which is what the above trials are doing) and then use data and theory to infer effectiveness. If we felt it necessary to study effectiveness, human challenge trials would be ideal in this situation as you can study gradually smaller doses with little risk to the patients. But given the urgency, immunogenicity trials should provide enough information to make decisions on the ground. To limit risk, one could do a half-dose on the second dose or one could do a half-dose in people under the age of 50. Both of these regimens would still create significant increases in supply. Recall that in 2018, facing a yellow fever epidemic and a shortage of vaccine, Brazil used 1/5th doses to break the epidemic.

There are no guarantees but the world is ignoring a potential trillion dollar bill lying on the sidewalk.

Hat tip for discussion: Witold and Amrita.

India Delays the 2nd Dose; Delaying 2nd Dose Improves Immune Response; Fractional Dosing

India has delayed the second dose to 12-16 weeks.

In other news, delaying the second dose of the Pfizer vaccine appears to improves the immune response (as was also found for the AstraZeneca vaccine). The latter is a news report based on a press release so some caution is warranted but frankly this was always the Bayesian bet since most vaccines have a longer time between doses as that helps the immune system. As Tyler and myself both argued, the short gap between the first and second dose was chosen to speed up the clinical trials not to maximize immunity. That was the right decision in the emergency but it was never the case that following the clinical trial regimen was “going by the science” no matter what Fauci said.

Many lives have been lost by not going to first doses first earlier, both here and in India.

Every country should move to a regimen in which the second dose comes at 12-16 weeks, even the United States, as this may improve the immune response and help other countries get a little bit ahead in their vaccine drives.

May I now also beat the drum some more on fractional dosing? Many people (not everyone) report that the second mRNA dose packs a wallop. I suspect that a half dose at 12-16 weeks would be plenty and that would free up significant capacity to vaccinate more people with first doses. We could also run some trials on half-doses for the young as a way to balance dosing and risk. Again this will matter for the rest of the world more than the United States but stretching doses in the United States will help the rest of the world and the arguments against stretching doses are now much diminished.

Alternative Dosing

Close-up medical syringe with a vaccine.

Alternative dosing is finally getting some attention. This story in Nature recounts some of the recent arguments and evidence:

Two jabs that each contained only one-quarter of the standard dose of the Moderna COVID vaccine gave rise to long-lasting protective antibodies and virus-fighting T cells, according to tests in nearly three dozen people1. The results hint at the possibility of administering fractional doses to stretch limited vaccine supplies and accelerate the global immunization effort.

Since 2016, such a dose-reduction strategy has successfully vaccinated millions of people in Africa and South America against yellow fever2. But no similar approach has been tried in response to COVID-19, despite vaccine shortages in much of the global south.

“There’s a huge status quo bias, and it’s killing people,” says Alex Tabarrok, an economist at George Mason University in Fairfax, Virginia. “Had we done this starting in January, we could have vaccinated tens, perhaps hundreds, of millions more people.”

…Sarah Cobey, an infectious-disease researcher at the University of Chicago in Illinois and a co-author of a 5 July Nature Medicine commentary supporting dose ‘fractionation’, disagrees about the need for time-consuming data collection.

“We shouldn’t wait that long,” she says. “People are dying, and we have historical precedent for making very well-reasoned guesses that we think are going to save lives.”

…According to a modelling study published by Tabarrok and other economists, such an approach would reduce infections and COVID-linked deaths more than current policies.

Addendum: The reason for doing the modeling study is precisely to take into account variants like Delta. Our modeling suggests that even with efficacy significantly lower than that suggested by Figure 1 in our paper, alternative doses of more effective vaccines would still provide significant reductions in mortality, even when new variants dominate. The benefits derive from vaccinating more quickly.

Dose Stretching for the Monkeypox Vaccine

Photo Credit: NIAD. https://www.flickr.com/photos/niaid/52103767506/

We are making all the same errors with monkeypox policy that we made with Covid but we are correcting the errors more rapidly. (It remains to be seen whether we are correcting rapidly enough.) I’ve already mentioned the rapid movement of some organizations to first doses first for the monkeypox vaccine. Another example is dose stretching. I argued on the basis of immunological evidence that A Half Dose of Moderna is More Effective Than a Full Dose of AstraZeneca and with Witold Wiecek, Michael Kremer, Chris Snyder and others wrote a paper simulating the effect of dose stretching for COVID in an SIER model. We even worked with a number of groups to accelerate clinical trials on dose stretching. Yet, the idea was slow to take off. On the other hand, the NIH has already announced a dose stretching trial for monkeypox.

Scientists at the National Institutes of Health are getting ready to explore a possible work-around. They are putting the finishing touches on the design of a clinical trial to assess two methods of stretching available doses of Jynneos, the only vaccine in the United States approved for vaccination against monkeypox.

They plan to test whether fractional dosing — using one-fifth of the regular amount of vaccine per person — would provide as much protection as the current regimen of two full doses of the vaccine given 28 days apart. They will also test whether using a single dose might be enough to protect against infection.

The first approach would allow roughly five times as many people to be vaccinated as the current licensed approach, and the latter would mean twice as many people could be vaccinated with existing vaccine supplies.

…The answers the study will generate, hopefully by late November or early December, could significantly aid efforts to bring this unprecedented monkeypox outbreak under control.

Another interesting aspect of the dose stretching protocol is that the vaccine will be applied to the skin, i.e. intradermally, which is known to often create a stronger immune response. Again, the idea isn’t new, I mentioned it in passing a couple of times on MR. But we just weren’t prepared to take these step for COVID. Nevertheless, COVID got these ideas into the public square and now that the pump has been primed we appear to be moving more rapidly on monkeypox.

Addendum: Jonathan Nankivell asked on the prediction market, Manifold Markets, ‘whether a 1/5 dose of the monkey pox vaccine would provide at least 50% the protection of the full dose?’ which is now running at a 67% chance. Well worth doing the clinical trial! Especially if we think that the supply of the vaccine will not expand soon.

Most Popular MR Posts of the Year!

As measured by page views here are the most popular MR posts of 2021. Coming in at number 10 was Tyler’s post:

10. Best non-fiction books of 2021

Lots of good material there and well worth revisiting. Number 9 was by myself:

9. Revisionism on Deborah Birx, Trump, and the CDC

TDS infected many people but as the Biden administration quickly discovered the problems were much deeper than the president, leading to revisionism especially on the failures of the CDC and the FDA. Much more could be written here but this was a good start.

Number 8 was Tyler’s post:

8. The tax on unrealized capital gains

which asked some good questions about a bad plan.

7. We Will Get to Herd Immunity in 2021…One Way or Another

Sadly this post, written by me in January of 2021, had everything exactly right–we bottomed out at the end of June/early July as predicted. But then Delta hit and things went to hell. Sooner or later the virus makes fools of us all.

6. Half Doses of Moderna Produce Neutralizing Antibodies

One of my earlier pieces (written in Feb. 21) on fractional dosing. See also my later post A Half Dose of Moderna is More Effective Than a Full Dose of AstraZeneca. We have been slow, slow, slow. I hope for new results in 2022.

5. A few observations on my latest podcast with Amia Srinivasan

Listener’s took umbrage, perhaps even on Tyler’s behalf, at Srinivasan but Tyler comes away from every conversation having learned something and that makes him happy.

4. The Most Impressive AI Demo I Have Ever Seen

Still true. Still jaw-dropping.

3. Patents are Not the Problem!

I let loose on the Biden administration’s silly attacks on vaccine patents. Also still true. Note also that as my view predicts, Pfizer has made many licensing deals on Paxalovid which has a much simpler and easier to duplicate production process (albeit raw materials are still a problem.)

2. A Nobel Prize for the Credibility Revolution

A very good post, if I don’t say so myself, on this year’s Nobel prize recipients, Card, Angrist and Imbens.

1. How do you ask good questions?

Who else but Tyler?

To round out the top ten I’d point to Tyler’s post John O. Brennan on UFOs which still seems underrated in importance even if p is very low.

Erza Klein’s profile of me still makes me laugh, “He’s become a thorn in the side of public health experts…more than one groaned when I mentioned his name.” Yet, even though published in April many of these same experts are now openly criticizing the FDA and the CDC in unprecedented ways.

UFOs going mainstream or Tabarrok’s view of the FDA going mainstream. I’m not sure which of these scenarios was more unlikely ex ante. Strange world.

Let us know your favorite MR posts in the comments.

The Most Important Act of the Last Two Decades?

A good case can be made that Project Bioshield is the most important piece of legislation passed in the last twenty years. Passed under President Bush in 2004, Project Bioshield’s primary goal was to create advance market commitments to purchase countermeasures for chemical, biological, radiological or nuclear agents (CBRN). Several billion dollars have been spent in this area promoting anthrax and smallpox vaccines and various antitoxins for botulism and nuclear threats. The record on these advance market commitments is mixed with some notable failures.

The second thing the act did is to reduce some paperwork requirements on purchases and research funding. Those seem fine although the simplified procedure is itself too complex and the amounts such simplified procedures apply to are too small, e.g.

The Project Bioshield Act authorizes the HHS Secretary to use an expedited award process for grants, contracts, and cooperative agreements related to CBRN countermeasure R&D Activity, if the Secretary deems a pressing need for an expedited award exists. The authority is limited to awards of $1.5 million or less.

The third aspect of the act was not considered a big deal at the time but is the one that has proved to be the most important. Project Bioshield created the Emergency Use Authorization (EUA). In other words, prior to 2004 the FDA had no clear legislative authority to authorize an unapproved vaccine, drug or device. Without Project Bioshield and the EUA procedure the FDA might have eventually found some way to authorize vaccines before full approval. Britain, for example, used a temporary authorization procedure. Or the FDA might have sped up full approval but given the FDA’s lethargic record it’s easy to imagine that this would have taken months longer than the EUA process. As a result, the EUA procedure created by Project Bioshield probably saved 100,000 or more lives.

Important Addendum: It’s also worth mentioning that the EUA procedure doesn’t just apply to approvals it also allows changes in dosage and labeling. Susan Sherman, the senior attorney with the HHS Office of the General Counsel, noted in 2009 that a drug that had been approved for individual health in a non-emergency might have to be used very differently for public health in an emergency and that the EUA process could be used to adjust to these differences:

“You can change the labeling. You can change the information. You can change the dosage. You can give it to populations for which wasn’t approved.” She continued, “In some sense we had to match up in practice a public health response where you might not have the precise labeling that your physician would prescribe to you. There are a lot of variables that are necessary for the public health responders that don’t necessarily match what the approved drug would look like if you just went to your physician and got it because you had that illness.

In other words, the EUA process was made to allow for procedures such as fractional dosing. It’s too late for fractional dosing in the United States (but we should use it for boosters) but fractional dosing remains a vital tool to deal with the global shortage of vaccines.

Self Recommending Links

1. I had a fun and wide-ranging conversation with Jonah Goldberg on the Remnant. We covered the economy, immigration, cyborgs and the Baumol effect among other topics.

2. Tim Harford covers fractional dosing at the FT:

The concept of a standard or full dose is fuzzier than one might imagine. These vaccines were developed at great speed, with a focus on effectiveness that meant erring towards high doses. Melissa Moore, a chief scientific officer at Moderna, has acknowledged this. It is plausible that we will come to regard the current doses as needlessly high.

3. The Brunswick Group interviews me:

Act like you’re in a crisis. That has been economist Alex Tabarrok’s advice since the start of the COVID-19 pandemic. Tabarrok was among the earliest and loudest voices arguing for urgency and risk-taking when it came to increasing rapid testing, investing in vaccine capacity, and employing flexible vaccine dosing. In hindsight, he has been proven regularly right when most health experts were wrong.

A Half Dose of Moderna is More Effective Than a Full Dose of AstraZeneca

Today we are releasing a new paper on dose-stretching, co-authored by Witold Wiecek, Amrita Ahuja, Michael Kremer, Alexandre Simoes Gomes, Christopher M. Snyder, Brandon Joel Tan and myself.

The paper makes three big points. First, Khoury et al (2021) just published a paper in Nature which shows that “Neutralizing antibody levels are highly predictive of immune protection from symptomatic SARS-CoV-2 infection.” What that means is that there is a strong relationship between immunogenicity data that we can easily measure with a blood test and the efficacy rate that it takes hundreds of millions of dollars and many months of time to measure in a clinical trial. Thus, future vaccines may not have to go through lengthy clinical trials (which may even be made impossible as infections rates decline) but can instead rely on these correlates of immunity.

Here is where fractional dosing comes in. We supplement the key figure from Khoury et al.’s paper to show that fractional doses of the Moderna and Pfizer vaccines have neutralizing antibody levels (as measured in the early phase I and phase II trials) that look to be on par with those of many approved vaccines. Indeed, a one-half or one-quarter dose of the Moderna or Pfizer vaccine is predicted to be more effective than the standard dose of some of the other vaccines like the AstraZeneca, J&J or Sinopharm vaccines, assuming the same relationship as in Khoury et al. holds. The point is not that these other vaccines aren’t good–they are great! The point is that by using fractional dosing we could rapidly and safely expand the number of effective doses of the Moderna and Pfizer vaccines.

Second, we embed fractional doses and other policies such as first doses first in a SIER model and we show that even if efficacy rates for fractional doses are considerably lower, dose-stretching policies are still likely to reduce infections and deaths (assuming we can expand vaccinations fast enough to take advantage of the greater supply, which is well within the vaccination frontier). For example, a half-dose strategy reduces infections and deaths under a variety of different epidemic scenarios as long as the efficacy rate is 70% or greater.

Third, we show that under plausible scenarios it is better to start vaccination with a less efficacious vaccine than to wait for a more efficacious vaccine. Thus, Great Britain and Canada’s policies of starting First Doses first with the AstraZeneca vaccine and then moving to second doses, perhaps with the Moderna or Pfizer vaccines is a good strategy.

It is possible that new variants will reduce the efficacy rate of all vaccines indeed that is almost inevitable but that doesn’t mean that fractional dosing isn’t optimal nor that we shouldn’t adopt these policies now. What it means is that we should be testing and then adapting our strategy in light of new events like a battlefield commander. We might, for example, use fractional dosing in the young or for the second shot and reserve full doses for the elderly.

One more point worth mentioning. Dose stretching policies everywhere are especially beneficial for less-developed countries, many of which are at the back of the vaccine queue. If dose-stretching cuts the time to be vaccinated in half, for example, then that may mean cutting the time to be vaccinated from two months to one month in a developed country but cutting it from two years to one year in a country that is currently at the back of the queue.

Read the whole thing.

The Becker-Friedman center also has a video discussion featuring my co-authors, Nobel prize winner Michael Kremer and the very excellent Witold Wiecek.

Two Vaccine Updates

First, in an article on new vaccine boosters in USA today there is this revealing statement:

Any revised Moderna vaccine would include a lower dose than the original, Moore said. The company went with a high dose in its initial vaccine to guarantee effectiveness, but she said the company is confident the dose can come down, reducing side effects without compromising protection.

Arrgh! Why wait for a new vaccine??? Fractional dosing now!

A microneedle patch for vaccines.

The same article also notes:

One of Moderna’s co-founders, MIT professor Robert Langer, is known for his research on microneedles, tiny Band-Aid-like patches that can deliver medications without the pain of a shot. Moderna has said nothing about delivery plans, but it’s conceivable the company might try to combine the two technologies to provide a booster that doesn’t require an injection.

The skin is highly immunologically active so you can give lower doses with a microneedle patch. The microneedles are sometimes made from sugar and don’t hurt. Microneedle delivery, however, can cause scars but I say apply the patch where the sun don’t shine and let’s go!

Second, Canada’s NACI has now endorsed mix and match for the AZ and Pfizer and Moderna vaccines. First Doses First has put Canada in very good shape (now ahead of the US in percent of the population with at least one dose) and this was always part of the FDF plan–delay second doses to get out more first doses and then, when supplies increase, give second doses, possibly with a better vaccine.

Cold Storage No Longer a Constraint

Yahoo: With little fanfare, the U.S. Food and Drug Administration gave Pfizer permission this week to store its COVID-19 vaccine in a typical refrigerator for one month — freeing the vaccine from the need to be shipped in cumbersome boxes stuffed with dry ice.

Among authorized COVID-19 vaccines, Pfizer’s vaccine was notorious for its ultra-cold storage requirements. Now, as the only vaccine authorized for children ages 12 to 17, this new flexibility could dramatically accelerate the effort to vaccinate America’s teens and adolescents.

Pfizer spent millions on its cold storage technology and now discovers that it isn’t strictly necessary–that wasn’t a mistake, Pfizer did the right thing–but it’s a good reminder of how new this technology is and also how the clinical trial decisions are not written in stone.

Straussian take: Investigate fractional dosing.

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