Today I’d like to address the issue of vaccination of individuals who have already been infected with the SARS-CoV-2 virus.
There is a growing consensus supporting the concept that SARS-CoV-2 immunization may provide better and more broad spectrum immune protection than infection alone.
While infection provides protective immunity for six months or more, the immunity to the spike protein, the protein that binds to human cells and facilitates infection, is less intense than the vaccine which only contains the specific binding portion of the spike protein.
These factors may limit the protection especially against variant SARS-CoV-2 virus. This is reinforced by reports of individuals being infected with variant viruses after prior COVID-19 infection. In contrast, there’s been no evidence that anyone has become infected after being fully immunized with the Pfizer or Moderna vaccines.
Given this, there has been much discussion on the proper approach to immunizing individuals who previously have been infected with SARS-CoV-2. Until recently, these folks have been immunized like everyone else. In fact, prior infection has not even been confirmed before vaccination. Despite this, several issues have come up.
First there is timing of the vaccine dose. You do not want to immunize someone too close to their natural infection because the immunity from the infection may block the ability of the vaccine to boost their immune response. In this situation, the antibodies produced by the infection will neutralize the vaccine before it can boost immunity. So most recommendations (and the CDC) are suggesting waiting about 90 days before attempting to immunize people after a COVID-19 infection.
This immunization is now perceived as a “booster” to the infection. This means your initial immunization was actually the infection and the vaccine serves as the second dose or booster. Therefore the recommendation now is not to include a second dose of vaccine for people who have already been infected.
The second issue is which vaccine to use as a booster post infection. There doesn’t seem to be an absolute preference for which vaccine to use despite the varied options around the world. My preference, however, given the high efficiency of the RNA vaccines, is that they might be most effective in boosting immunity especially to variant viruses. So while the best answer is always to get immunized with whatever vaccine you can, it may be optimal to get immunized with either the Pfizer or the Moderna vaccines.
I strongly believe that we should be screening everyone who potentially has a history of a prior COVID-19 infection when we vaccinate them. Because there is only spike protein in the vaccine, we can confirm prior infection by screening for antibodies to other viral proteins, usually nuclear capsid protein. This will allow a rational plan for the vaccination of individuals and enhance the prevention of COVID-19 infection in the future.