Booster shots and the current Covid-19 Delta wave

Switzerland is now offering a covid19 booster shot to to the 65+ and at-risk who has had their two covid19 vaccinations at least six months ago. It may soon be extended to all adults. I had my third shot last Thursday with no side effects (not even a localized sore spot) and was surprised to receive a Pfizer booster after being fully vaccinated earlier this year with the Moderna vaccine. The mRNA in both vaccines encode the same S-2P protein which differs from the covid19 spike protein by two amino acids only. These stabilize the spike protein so that it can train the immune system before it enters the host cell. I’ve been reading up on booster shots and will try to provide a brief summary below. If you want citations and more detail on the studies, see my professional blog here.

A large study of 1.14 million Israeli adults, aged 60 years and over who had received two Pfizer doses at least 5 months earlier, found that a third shot reduces the risk of infection by the dominant Delta variant by a factor of 11 compared to fully vaccinated people who have had two shots.  Receiving a different vaccine type as I did, further reduces the risk by around 30% or more. The booster shot lowers the risk of severe illness even more, by a factor of around 20 compared to those who have had two shots only.

Continue reading