A few months ago, we believed recovering from Covid-19 meant the chances of getting the virus again so soon were low. Scientists thought we were protected for at least six months after the initial infection.
But now, as the hyper-transmissible BA.5 variant whips around the world, more and more reinfections are being detected in people who’ve already had Covid once, if not twice, before.
“Reinfections are due to several reasons, including more relaxed safety precautions such as masking and social distancing, as well as declining antibody levels and additional viral mutations, which can result in immune escape by omicron sub-variants,” Pablo Penaloza-MacMaster, an assistant professor of microbiology-immunology at Northwestern University Feinberg School of Medicine and advisor to the Illinois Department of Public Heath, tells HuffPost.
In addition to SARS-CoV-2, there are four other coronaviruses that circulate and cause the common cold. These viruses are known to reinfect people after an average of about 12 months. Though there was hope that we’d eventually gain herd immunity against Covid, it appears that SARS-CoV-2 is behaving like the other coronaviruses that we’re exposed to year after year.
“Extrapolating from data with other coronaviruses, reinfections with SARS-CoV-2 variants are expected,” Penaloza-MacMaster says, pointing out that BA.5 also has several mutations on the spike protein that make it easier for the coronavirus to enter and attach to our cells. These mutations help it appear somewhat invisible to the antibodies that our body produced during previous infections and vaccinations.
“That sets up for higher risks for people being less protected against getting any infection,” says Albert Shaw, Yale Medicine infectious diseases doctor and professor of medicine at Yale School of Medicine.
It’s tough to pin down how soon people are susceptible to reinfection, Shaw says. That timing largely depends on when you were last vaccinated or boosted, the state of your immune system, your age and presence of underlying health conditions.
The variant you were last infected with, and when, also impacts your risk of reinfection. A pre-print study from Qatar recently found that effectiveness of a pre-omicron infection (like delta or alpha) against a BA.5 infection was about 28% whereas effectiveness of an omicron infection against a BA.5 infection was closer to 80%.
This most likely has to do with how many vaccines people had at the time and when people got infected, according to Julie Parsonnet, an infectious diseases epidemiologist with Stanford Medicine.
“If you got infected with Delta, you were infected a relatively long time ago, and if you were infected with Omicron, you were infected relatively recently and that may mean your immunity may be a little bit better just because it hasn’t waned over time,” Parsonnet says.
Shaw says most people are still probably well-protected for a few months, but beyond six months, the immunity that prevents symptomatic infections is likely waning substantially. Some people have been reinfected in as little as four weeks.
According to Parsonnet, no matter how many times someone has been infected, there is no way to ensure they are 100% safe from getting Covid again. “I don’t think there’s anyone out there who can say, “I’m immune – I’m just not going to get it,’” Parsonnet says.
Though we can’t prevent reinfections (yet), the vast majority of them will be less severe since the body has memory immune responses that will likely stay intact for years. Penaloza-MacMaster says that though symptoms depend on the person, they may involve headache, difficulty breathing, coughing, fatigue, fever, among others – or no symptoms at all. The symptoms also depend on the variant and the amount of virus a person is exposed to, he adds.
At the same time, reinfections – even if they’re less severe – may lead to new health issues. A pre-print study from Washington University School of Medicine recently found that repeat Covid infections increase the risk of persistent health issues – like lung and heart problems and digestive or kidney disorders – after the infection. “The potential for some unpredictable consequences for these organ systems probably increases with subsequent reinfections as well,” Shaw says.
The vaccines and boosters still do a good job at keeping us safe from serious outcomes, even with the new variants. Vaccination triggers a more robust immune response against severe outcomes from Covid-19, which is why it’s so crucial to stay up to date on booster shots.
“It’s clear that the vaccines and prior infections still protect against severe illness and serious illness, so that’s the good side,” Parsonnet says.
Experts are still learning about Covid-19. The information in this story is what was known or available at the time of publication, but guidance could change as scientists discover more about the virus. To keep up to date with health advice and cases in your area, visit gov.uk/coronavirus and nhs.uk.