A: No. There is no evidence of a hyperimmune response in COVID-19 vaccinated people later exposed to the virus.
👉🏽 TL;DR: Exposure to SARS-CoV-2 after having received a COVID-19 vaccine does not result in an exaggerated or dangerous immune response. Hundreds of millions of people globally have now received one of the approved COVID19 vaccines. Thus far, there are NO reports of people developing a hyperimmune response to infection after vaccination.
❓Why is there concern about hyperimmune response after vaccination?
The concern is linked to a phenomenon known as Antibody Dependent Enhancement (ADE) https. See DP post on ADE here. In ADE, antibodies are made against a lot of viral proteins, either after natural infection or vaccination for a specific virus. Some of these antibodies can neutralize the virus whereas others do not. These ‘non-neutralizing’ antibodies can stick to the virus and help it infect cells, rather than helping to destroy it. The antibody-virus complex can get stuck in airways, or they can prompt infected cells to make proteins called ‘cytokines’ that drive inflammation.
ADE is not common, but has been seen both for Dengue fever and RSV (Respiratory Syncytial Virus), which causes severe respiratory disease in infants. People with dengue virus who get re-infected can get worse disease, including blood clots and a sudden loss in blood pressure. During initial small clinical trials for an RSV vaccine, children who received the vaccine and later contracted RSV infection got a lot sicker than unvaccinated children. This was quickly identified and the trial stopped. These outcomes were due to an exaggerated and inappropriate immune response to the second infection (dengue virus) or to the first infection after vaccination (RSV). Because ADE exists and SARS-CoV-2 was a brand new virus, an important early question was whether we would see a similar issue with COVID19 re-infection or vaccines.
🤔 Should we worry about a hyperimmune response to SARS-CoV-2 following COVID-19 vaccination or re-infection?
Scientists were very mindful of the experience with dengue virus and RSV during the development of COVID-19 vaccines. The COVID19 vaccines are designed to make antibodies specifically to neutralize the virus. This strategy helps to limit non-neutralizing antibodies responsible for hyperimmune immune responses in dengue infection. In all of the COVID-19 vaccine trial data, there were no cases of vaccinated people (after either one or two doses) who got infected and had a hyperimmune response.
Also, HUNDREDS OF MILLIONS of people have now been vaccinated, with many likely exposed to the currently circulating SARS-CoV-2 variants; however, there have been no reports of hyperimmune among vaccinated people. Millions more have been re-exposed to SARS-CoV-2 after previous infection, with no evidence of hyperimmune response upon re-exposure to natural infection.
We know that the prospect of hyperimmune response sounds scary, but it’s important to remember that WORSE disease is something easy to spot in the data, especially with so many people vaccinated or exposed to re-infection after natural infection. If ADE were a problem for SARS-CoV-2, it would have been very obvious early on in the pandemic and clinical trials.
The weight of this evidence makes us confident that a hyperimmune response to infection after vaccination is extremely unlikely. The ability of the vaccines to prevent infection and severe disease however, is well-established. Scientists continue to work on understanding the breadth and depth of the immune response to COVID19 vaccines and how well these vaccines work against SARS-CoV-2 variants.
❗Bottom line: Exposure to SARS-CoV-2 does not provoke a hyperimmune response in COVID19-vaccinated people.
Love,
Those Nerdy Girls
📖 Additional reading:
Vaccine researchers mindful of immune-enhancement
COVID19 infection and vaccination
Vaccine side effects in COVID19-recovered people
