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.


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