How Long Will the Protection From COVID-19 (Coronavirus) Vaccines Last?

Dec 19

With the first administrations of COVID-19 vaccines, we have now reached a turning point in the pandemic. Now that we have several COVID-19 vaccines available, one important question that we will need to answer is how long will the protection from these vaccines last? People who had COVID-19 infection have generated COVID specific antibodies in their bodies after recovering from the illness. Protection comes when these virus-specific antibodies are formed, but it begs the question of whether it will prevent possible reinfection? The answers to these questions can be understood by looking at how our immune system works.

While antibodies are important, they are not the only part of our immune defense mechanism. Antibodies latch on to the surface of the viruses, block them from invading the cells in our body. In general, the more antibodies you generate, the stronger the immune defense is. Another part of our immune system, also protecting against foreign invaders (such as the coronavirus), is called the cell-mediated immune response. This cell-mediated immune system works in parallel with the antibody response to mount an optimal defense against the virus. The added advantage of the cell-mediated immune system is a memory function, which allows the immune system to quickly spring into action should the virus re-enter the body at a later time point. Both the viral infection and the vaccine will generate the two types of responses of the immune system.

It is quite normal to see some decline in antibodies overtime after infection with the virus and also potentially after vaccination, but that doesn’t mean that there’s no protection. However, based on some cases we saw that it is possible to get COVID-19 more than once, though it is a rare and milder occurrence. It could be, though not sure, that Covid-19 behaves more like a seasonal cold or flu viruses, for which we don’t retain long-term protection or immunity. If this is the case, then we are potentially looking at repeated vaccinations for COVID-19 just like the seasonal flu vaccines.

Researchers don’t know yet how long the COVID-specific antibody protection will last after natural infection, or after vaccination. The World Health Organization (WHO) recommends that a minimum of six months of protection would be acceptable. It’s hard to predict accurately at this point, especially since the clinical studies only began giving second doses of the vaccine 4 months ago. Some experts predict that the vaccines will provide months to years of immunity against COVID-19 and may require annual booster shots for continued protection.

To know for sure, scientists will need to look closely at and collect more data from the clinical trials. This question of the duration of antibody protection will be part of ongoing studies, which can take several months or even more than a year to see if the antibodies last that long in vaccinated individuals and/or prevent a COVID-19 infection.

Today we have examples of vaccines against other infectious diseases that generate a much stronger and longer-lasting response than naturally contracted viral infection. We are hoping that the COVID vaccines will behave similarly. Currently, we only have three vaccine candidates, from Pfizer and BioNTech, Moderna, and AstraZeneca and the University of Oxford, that showed good safety and efficacy data from their respective clinical studies. All the vaccine makers, however, will continue their trials well beyond regulatory authorization in pursuit of collecting additional important information. These trials will extend for an additional 2 years when study participants will continue to report about long-term safety and efficacy. If, for instance, participants who were vaccinated go on to develop Covid-19 after a year, we will know how long the immunity lasted and whether it is necessary to receive annual booster shots to help sustain protection against coronavirus infection.

It is also possible that reinfections simply occur when people didn’t get sick enough to develop strong immune responses against the coronavirus. If that is true, then there’s a good chance that the vaccines could help generate a stronger immune response, protecting those people for a long period of time.

But guess what we do know about the duration of protection from the mRNA COVID-19 vaccines? The first set of human volunteers who received the mRNA vaccines was back in March of 2020, in the initial safety study. These volunteers are still protected. This means that we have a minimum of nine months of protection to date, and possibly more—hopefully three to four years to be consistent with animal data. We know that in mouse studies, 2 doses of mRNA vaccines against coronavirus protected mice for 13 weeks, which is typically equivalent to years in humans. This may not seem very long but would be an incredible win in the midst of this deadly pandemic!

Disclaimer: Vaxtherapy is NOT affiliated with any of the pharma/biotech companies working on COVID-19 vaccines. The purpose of this post is to provide education and awareness from a virologist’s independent perspective based on available facts and data.

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