During the winter wave of COVID-19, it felt like coronavirus was everywhere. Colder weather pushed people inside where the virus can linger in the airand the growth-dominant omicron variant of SARS-CoV-2, the virus that causes COVID-19, had the cumbersome ability to evade some immune responses (SN: 18/5/21). That meant it both vaccinated or previously infected humans were more susceptible to becoming infected than they were with previous coronavirus variants. This should perhaps not have come as a surprise, as the primary goal of vaccines is to prevent serious illness and death (not to prevent infection at all, what is called sterilizing immunity). Still, omicron took everyone on guard.
Eventually, weeks after the COVID-19 cases skyrocketed, they continue to trend downward in most parts of the United States and around the world. Every time chance falls, I hold my breath in the hope that signs of the resurgence will not show up. So far, so good – for now. I might be able to let that breath out soon, at least a little bit. (Although cases in New Jersey, where I live, appear to be plateauing at levels close to the top of last summer’s delta wave.)
The majority of winter’s COVID-19 cases were caused by a subvariant of omicron christened BA.1. Researchers are now keeping an eye on its close siblings, an omicron subvariant called BA.2. Although cases are generally falling, BA.2 is increasingwhich accounts for an estimated 4 percent of new cases in the United States in the week ending Feb. 19.
BA.2 concerns researchers because it is slightly more transmissible than BA.1, which may prolong the current increase, and it also has some mutations other than BA.1. Both BA.1 and BA.2 can avoid immune responses by evades virus-attacking antibodies triggered by vaccination or infection with other variants, and some of the differences in BA.2 may mean that it can avoid antibodies formed after a BA.1 infection (SN: 21/12/21). So far, that is not what the researchers see. Instead, although these types of re-infections can occur, they are rare, reports a team from Europe in a preliminary study published on February 22 on medRxiv.org. Re-infections with BA.2, the team found, were most common in young, unvaccinated people who were not hospitalized. Time will tell how long this protection lasts and how it can cope with future variants or sub-variants.
This is not the first time we are worried about reinfections. An eternity ago in pandemic time, in early 2021, the emergence of the alpha, beta and gamma variants triggered concern that more people may soon be confronted with a second round of COVID-19. So last February, I interviewed epidemiologist Aubree Gordon of the University of Michigan in Ann Arbor to hear her thoughts on what variants can mean for the pandemic as a whole (SN: 2/5/21).
Back then, our understanding of reinfections was in its infancy. Studies have suggested that the beta and gamma variants could evade parts of the immune system, making reinfections possible. But we did not know how common reinfections were, or whether a second round of COVID-19 could be less severe than the first. Meanwhile, vaccine rollout in the United States was on the rise, and many people were desperately searching for the first doses. Last year, Gordon, who has studied corona reinfections, said the new variants could prolong the pandemic. But she was quick to remind me that even in the light of variations, pandemics always end.
Fast forward to February 2022. Vaccines are more widely available (although there are still access issues and some people do not want shots) and we are certainly no spring chickens when it comes to face-offs with new varieties. But because the pandemic is a time warp, I decided to catch up with Gordon now to see if her mindset has changed since February 2021. Our conversation has been edited for length and clarity.
Garcia de Jesús: What have we learned about reinfection over the last year?
Gordon: One of the things we learned about reinfection or [vaccine] Breakthrough is that once people have the second exposure – be it their first is vaccination and their second is infection, or their first is infection and second is vaccination – people generate “hybrid immunity.” People generate a wider [immune] answers that will help protect them from future infections. It is not going to sterilize immunity against all variants that occur, but it will definitely help reduce the likelihood of people getting infected or re-infected with each variant. And when they become re-infected, they will be milder infections.
Garcia de Jesús: Last year you said we may or may not need booster shots. What are your thoughts now?
Gordon: Our perception of boosters has completely changed. It became clear that boosters would help. They would help slow down the transmission. They would help reduce the severity of people having breakthrough infections. I think one generally feels that an omicron-specific booster is needed because being vaccinated and boosted with the original virus strain is not very effective in preventing omicron infections.
We need to look to the future. I think one of the big questions with an omicron-specific booster will be what effect that booster will have on someone who has already been vaccinated or even vaccinated and boosted in the past. Is it just to boost immunity to omicron? Or do you see them developing broader immunity? By boosting with another variant, you may be able to generate broader immunity to not only protect against omicron, but also briefly protect against any future variants circulating.
Garcia de Jesús: While states are dropping mask mandates, we are leaving the pandemic phase of this viral outbreak. Is it true?
Gordon: I think it would be a mistake to completely let go of control at this point. We are not through it, we are not at the endemic level [when the virus normally circulates at some baseline amount]. But I think we are in a period of transition.
If you look back at flu pandemics, for example, there has been a transition period: The first or two years with a very high toll, but then beyond that, [transmission] typically stays higher for a few years. I think at this point that we are in a phase where most countries – not every single country, but in most – a majority of the population have some degree of immunity. What the transition period looks like for SARS-CoV-2, the virus that causes COVID-19, really depends on the severity of infections and how many exposures we need to get down to an endemic level. A single exposure seems to have really reduced the severity, but maybe it did not get it down to the endemic level where you grew up being exposed to this virus all your life. The length of this transition period, and how painful it is, will really depend on the severity of reinfections that occur over time.
Garcia de Jesús: What will the endemic phase of the pandemic look like?
Gordon: Endemic is a period in which the virus has reached a “normal level.” You have a high level of population immunity, and [the virus] still causing a certain level of serious illness. We do not know what it looks like yet. We do not know if the severity of this virus in the endemic phase will resemble a seasonal coronavirus [that causes a cold] or if it comes to resemble the severity of the flu [which can kill tens of thousands of people on average per year in the United States] or more severe than influenza. We actually have to get to where it is on an endemic level before we know it all.
And the other thing is the infection rates. We know for seasonal coronavirus that people get re-infected really often – on average probably around every three years, but it can happen as soon as six months later, even in people who have been exposed to it throughout their lives. At the beginning of the pandemic, the entire population was naive about this new coronavirus. We have built up immunity over time so the transmission remains quite high. It will diminish as people build immunity, but we’ll see. We may need annual boosters or regular boosters. Maybe we can come up with a broader protective vaccine that lasts longer – that would be great.
Garcia de Jesús: Do you feel more optimistic or pessimistic than last year?
Gordon: Honestly, I’m about the same. The only thing that made me a little pessimistic… was in studies we did in Nicaragua. We got a big wave in 2020, about 60 percent of the population in that study was infected. So we went ahead and had another big wave in 2021, probably of gamma and delta. One thing that made me a little more pessimistic about the situation was that the severity of recurrent infections was higher than I expected… but I always thought people needed at least two exposures [to the virus] before we get near an endemic level. Maybe even more than two, we do not really know. We have omicron in Nicaragua now, so we have a large population that has already had two or three exposures, because a lot of them are also vaccinated now. We’ll see what happens during this omicron wave.
Garcia de Jesús: We all really want this to be over. How do we know that?
Gordon: I think people are confused about when a pandemic will end. As I said, it is a transition period. Instead of thinking of it as a dimmer switch – at the top is a pandemic, and then you slide down to the bottom, which is endemic – people want it to be a turned-off switch. Like “oh, it’s a pandemic, and now it’s over. We’re in an endemic phase.” But unfortunately we are not there yet. We will slowly slide towards an endemic phase.