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How coronavirus variants can boost reinfection and shape vaccination efforts

Vaccine implementation in the United States has been undeniably slow. And while we wait, new variants of coronavirus are emerging that increase the urgency of controlling the pandemic. Some variants, including those first identified in Brazil, South Africa, and the United Kingdom, have mutations that help the coronavirus evade parts of the immune system, increasing the spectrum that some people may face a second round of COVID-19.

All of this can make you feel like the pandemic has reached a full circle and that we are back where we started. But even in the face of possible reinfections, the world has at its disposal a tool that did not exist a year ago: effective vaccines.

Pfizer and Moderna shots have been allowed in the United States since December 2020. Vaccines developed by Novavax and Johnson & Johnson have recently announced promising results (SN: 28/01/21; SN: 29/1/21). On February 4, Johnson & Johnson became the third company to apply for emergency use authorization in the United States for its COVID-19 vaccine.

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And preliminary data from AstraZeneca suggest that a single dose of its vaccine may reduce the number of people who test positive for coronavirus by 67 percent, possibly reducing the spread of the virus in the community, researchers reported Feb. 1 in Preprints with the Lancet. Brake transmission is the holy grail of vaccine efficacy: this would give the coronavirus less chance of acquiring potentially dangerous mutations (SN: 27/01/21). This, in turn, could finally reveal the end of the pandemic.

Meanwhile, researchers are understanding the threat of known mutations. Even if someone has antibodies to the coronavirus (through a natural infection or a vaccine), some mutations can impede the ability of the antibodies to attach to the virus and prevent it from infecting the cells. Although antibodies are only part of the immune system’s arsenal for removing viruses from the body, the ability of variants to dodge immune proteins could put people who have already recovered from a COVID-19 attack from becoming infected again.

The first confirmed reinfection with SARS-CoV-2, the virus that causes COVID-19, was reported in August (SN: 24/08/20). There have been some documented cases of reinfection with new variants as well – including in Manaus, Brazil and on an Israeli traveler to South Africa – although some details remain unclear.

Reinfections are difficult to demonstrate. Doctors need genetic testing to show that a different strain of coronavirus caused each case of infection. What’s more, it’s possible that some people will never show symptoms and are unaware of the second infection. As a result, researchers still do not know how often people become infected with the coronavirus.

To explore what the emergence of new variants for reinfections, vaccines, and the pandemic might mean, Science News spoke with Aubree Gordon, an epidemiologist at the University of Michigan in Ann Arbor. This interview was edited for brevity and clarity.

SN: What have we learned about reinfection since August?

Gordon: We know they happen (reinfections). We don’t know much beyond that. There are a number of studies out there and there have been reports of reinfection cases, but at this time we still don’t know how common they are. What you would expect to see with reinfections is that as people go further than having their first infection, you would see more reinfections. But of course, at this point, we’ve been in the pandemic for a little over a year so there hasn’t been much time for a lot of people to reinfect themselves yet.

SN: Why wasn’t there enough time? Why do reinfections occur?

Gordon: Reinfections occur for a variety of reasons. But usually, it’s because someone no longer has enough immunity to the virus to prevent them from becoming infected.

If you have the same virus (no mutations), it is possible that people will become infected again because they did not make a very strong response to the virus the first time they became infected. Or maybe they made a strong response, but that response diminishes or diminishes over time, to the point where it’s not protective against contagion again.

Another way reinforcements occur is that the virus can change. If changes occur in the virus so that its antibodies no longer recognize the virus or some areas of the virus, at least reinfections can occur. Particularly for SARS-CoV-2, those (changes) could be its peak (the protein that the virus uses to break down in a cell).

The same goes for the flu on a fairly regular basis. The virus changes. Because the virus changes, our bodies do not recognize it and then we can reinfect ourselves with the virus.

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SN: What do we know about the role that new variants will play in reinfection?

Gordon: I definitely think the reports of reinfections are worrisome. But I think we need to find out how common these reinfections are in front of people we haven’t had before (COVID-19) and look at what the risk is.

Are people (reinfected) not protected (from the new variants)? I guess that’s probably not the case. My guess is that a lot of people who already had SARS-CoV-2 are probably still partially protected or not as protected. They may be more likely (to become infected again with the new variant) than the original virus. But if you compare them to people who have never had COVID-19 before or don’t have vaccine antibodies, you would still see a significant amount of protection. But we don’t have that data yet.

We also don’t know how serious those reinfections are. Researchers often capture the most serious cases – the tip of the iceberg – and that doesn’t necessarily give a complete picture of what’s going on. We have certainly seen a number of individual case reports with severe reinfections, but most serious cases will have the best access to evidence (which may over-represent how often this happens).

SN: If vaccines slow down transmission, how does that help?

Gordon: The availability of additional vaccines, such as the AstraZeneca vaccine, will speed up the vaccination process. And if vaccines reduce transmission, they are also very good news. (Fewer cases mean fewer opportunities for the virus to mutate).

Even before the advent of variants, it was critical that we vaccinate as many people as possible as quickly as possible and the variants only amplified that. High levels of SARS-CoV-2 transmission combined with a large proportion of people with pre-existing immunity to the original virus could trigger new variants. It also gives advantage to existing variants that have changed enough for pre-existing immunity to stop being so protective.

SN: What does all this mean for the immunity of cows and vaccines?

Gordon: It will be very difficult to achieve herd immunity if you have a very high reinfection rate in people without immunity to new variants.

I recently heard several people in my personal life express thoughts like, "Oh my, is this pandemic going to end?" Will we live like this forever? "And that is unlikely.

What we will probably find is that (reinfections) will continue to occur as the variants become more prevalent. Reinfections are likely to occur more often, especially as people move away from the original infection.

But I think our main concerns are serious cases and deaths. We can still see transmission even if everyone has immunity to the original virus. But the important thing is to ask how are (the symptoms) of the cases (of reinfection). I think everyone, myself included, is hopeful that we will see a drastic reduction in the severity of cases when comparing reinfections with a first infection.

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Certainly, some lab data suggests that vaccines may not work as well against variants. But for the Novavax vaccine, although it was less effective in preventing symptomatic SARS-CoV-2 infection in South Africa, where variant B.1.351 is very prevalent, it was still 100% effective against serious diseases. I think that’s something important that people have to pay attention to.

The reason we all change our lives as we have and have all the measures (such as the use of masks and physical distancing) is because COVID-19 is causing hospitalizations and deaths. It’s causing serious illness, it’s causing serious side effects, and (avoiding them) is what really worries us.

Vaccination companies are already beginning to study the possibility of making a shelter or a second vaccine. We could end up with a bivalent vaccine, for example, that has both the original strain and one of the (viral) variants that is best bypassed by the immune system.

SN: So when will the pandemic end?

Gordon: It’s going to be a little longer than it would be without those variants coming up. But pandemics always end in the end.

We can look back on flu pandemics; you usually have one or two years of circulation before enough immunity to the virus builds up. People may continue to become infected with the virus, but the infections are not as severe. And you don’t have as many people infected in a given year because of pre-existing immunity.

I think the timeline (pandemic) with the introduction of variants may be a little longer. But finally, I think we’re going to get to a place where SARS-CoV-2 is endemic, a human coronavirus (which circulates normally). Depending on the severity of the reinfections and the duration of immunity generated by the vaccines, we may or may not need additional booster vaccines for SARS-CoV-2 in the future.

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