I’ve Already Got COVID. Should I Get Vaccinated?
A natural question asked with respect to vaccination is whether a vaccine is necessary if one has already recovered from COVID. If I already have natural immunity, do I really need a vaccine? Two studies, published in the Lancet on February 25, answer in the unequivocal affirmative.
The first study examined healthcare workers in the UK who received the Pfizer/BioNTech vaccine and compared the antibody response of those who were previously infected or uninfected with SARS CoV-2. The healthcare workers who were previously infected with SARS CoV-2 had antibody responses that were way higher than that of natural immunity. The antibody responses were also higher than the post-vaccine antibody levels of those who were previously uninfected.
That said, antibodies — part of the humoral immune system — are not the only part of the immune response. There is also a T- and B-cell component, part of the cellular immune system. Enter the other study.
In this study, researchers also studied healthcare workers who received the Pfizer/BioNTech vaccine in the UK. Here is what they reported:
In summary, we show that individuals with previous SARS-CoV-2 infection generate strong humoral and cellular responses to one dose of BNT162b2 vaccine, with evidence of high titres of in-vitro live virus neutralisation. In contrast, most individuals who are infection-naive generate both weak T-cell responses and low titres of neutralising antibodies.
This research has two implications: (1) Vaccination is extremely important, even in people who have had COVID in the past. In essence, it acts as an immune response booster; (2) Two doses of the vaccine is essential, as the studies showed weaker immune responses after just one dose.
It is tempting to just give people one dose so that more people can get the vaccine. Yet, the studies show that this may not be advisable. Indeed the authors say as much:
Despite the difficulty of extrapolating immunological data to clinical protection, our findings raise important issues that warrant consideration when determining optimal use of vaccine supplies. Firstly, those with serological evidence of previous disease at baseline mount robust antibody and T-cell responses after a single dose of vaccine. Conversely, some infection-naive individuals mount very little demonstrable response to single-dose vaccination, which might not provide sufficient immunity to protect from clinical disease or viral shedding, and might not persist for a 12-week delay until second vaccine is administered.
So, bottom line: getting the vaccine is very important, even if you got COVID previously. The vaccines we have are safe, they are effective, and they are a sure fire way we can get out from under the darkness of this pandemic.