Question: In our continuing talks with my sister-in-law about vaccination, she says she believes she has had Covid before. What’s the risk of reinfection? I have heard it’s low but would like to hear the data.
Answer: I have a few issues with the premise of this question. First, if your sister-in-law believes she has had COVID before, it sounds like that belief was never confirmed (e.g. with a positive test), in which case it would be safest to assume that she has never been infected. Second, even if she has been infected, we don’t know how long her immunity lasts. Third, we know that vaccination is a safer way to build protection than (re)infection. CDC recommends that everyone who is eligible be vaccinated, regardless of whether they have already had COVID (see below paragraph). All that said, let me get back to your question! Here’s a rundown of some of what we know and don’t know about reinfection:
- Reinfection is possible, though relatively rare. It’s difficult to know just how rare reinfection is because it’s difficult to measure. (see Q&A of 11/21)
- We have limited data about reinfection by variant of concern. According to an article published earlier this month in JAMA, Neutralizing Antibodies Against SARS-CoV-2 Variants After Infection and Vaccination, antibodies produced by previous infection and vaccination are protective against the new B.1.1.7 variant (UK variant). However, evidence is emerging from Brazil that reinfection with the P.1 variant has occurred and may be driving the resurgence of cases.
- Reinfection can result in milder or more severe disease as compared with the initial infection. (see Q&A of 10/14)
- Risk of reinfection seems to increase with age. (see Q&A of 3/18)
- Neutralizing antibodies produced by previous infection and vaccination are protective for several months, however antibodies after infection vary a good deal from person-to-person. (see this paper published in Science and this one published in JAMA)
CDC’s guidelines for vaccination after infection: “Yes, you should be vaccinated regardless of whether you already had COVID-19. That’s because experts do not yet know how long you are protected from getting sick again after recovering from COVID-19. Even if you have already recovered from COVID-19, it is possible—although rare—that you could be infected with the virus that causes COVID-19 again. Learn more about why getting vaccinated is a safer way to build protection than getting infected.”