Thread by @NYCHealthCommr

At @nycHealthy, our recommendations for New Yorkers are grounded in science. That’s why we have been recommending ALL New Yorkers get vaccinated against #COVID19, even if you’ve been infected before or have antibodies. 🧵

We've received several questions from people who ask why vaccination is necessary if they’ve already had COVID-19 — aren’t they protected due to “natural immunity”? The bottom line is clear: your best protection is vaccination. The evidence ⬇

Although people who have recovered from #COVID19 may have some level of protection, there are many factors that influence just how much protection this affords.

Those factors include how much virus they were exposed to, how severe their illness was, and characteristics unique to that individual's immune system.

This study found that strength of immune response varies by severity of COVID-19 disease: ncbi.nlm.nih.gov/pmc/articles/P…

The real-world choice that people with prior #COVID19 infection face is whether or not to get vaccinated.

Comparisons between "natural" (or virus-induced) immunity and vaccine-induced immunity are less helpful than studies that compare protection between unvaccinated and vaccinated people with prior infection.

We looked at the data for New Yorkers previously diagnosed with #COVID19 and found that unvaccinated residents were *2.3 times* as likely as fully vaccinated residents to be reinfected during the period in which delta has been the dominant variant (data not yet published).

At the national level, peer-reviewed evidence from @CDCgov reinforces these findings regarding how vaccination offers significant protection against reinfection: cdc.gov/mmwr/volumes/7…

Another study showed that the neutralizing activity of antibodies (antibodies' ability to inactivate the virus) against #COVID19 variants of concern was greater in those who received a COVID-19 mRNA vaccine compared to those who were not vaccinated. nature.com/articles/s4158…

So while we don't know how protective virus-induced immunity is alone, we do know reinfection occurs, and it may be more common due to the characteristics of the delta variant.

Meanwhile, vaccination is safe—and studies also show that it strengthens immunity for those who had prior infection nature.com/articles/s4158…

We learn more about #COVID19 every day, and recommendations can be calibrated and modified based on new scientific information. Using the evidence we have right now about benefits and risks of vaccination, regardless of prior COVID-19, the choice is clear: Get the shot!