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.