Yes, the Third Dose Is Effective Against Omicron

But we have to understand what effectiveness means. Here’s some vaccine effectiveness data from the UK Health Security Agency that seems to jibe with other studies:

Screen Shot 2022-01-23 at 10.15.53 AM

Even after several months, people with three doses are 55-65% less likely to be infected, and this could be an underestimate (though not a huge one)*. That’s a good intervention! But there’s a problem.

That’s probably** not good enough for vaccination by itself to prevent spread–though it can protect individuals, especially in combination with other measures (e.g., masking, better ventilation, and so on). If R0 of Omicron is eight (in the absence of any measures including vaccination, one infected person will infect eight others), we simply won’t get there with the current three dose strategy. That said, it will offer non-immunocompromised individuals substantial protection, which will slow the spread down, and, if enough people do contract Omicron, that in conjunction with enough people who are uninfected with three doses, might get us to where Rt is less than one (meaning we won’t have sustained chains of transmission).

Keep in mind, while I’ve been discussing symptomatic infection, even two doses dramatically lowers the odds of hospitalization and death. So please get vaccinated, and, if you’re eligible, get boosted.

And this isn’t a lost cause, if we’re willing to do other things to limit the spread of Omicron, we can avoid the worst, so there’s no need for ‘endemic fatalism.’

*There are likely some people in the unvaccinated, PCR-negative group who have been infected previously, though it’s unclear how much protection that would provide or how many of them there are, but that means the unvaccinated baseline isn’t as ‘naive’ as an entirely unvaccinated and uninfected comparison population.

**It’s biology, so who knows though….

This entry was posted in COVID-19. Bookmark the permalink.