Unlike the beginning of the pandemic, COVID-19 reinfections are no longer uncommon, with more new variants emerging and leading to questions about immunity.
The omicron variant has led to a major shift in "natural immunity," with many who had previously been infected susceptible to reinfection with the variant, as well as its faster spreading subvariants, BA.4 and BA.5.
In May, Chicago Department of Public Health Commissioner Dr. Allison Arwady said data has shown that most people infected with COVID are protected from the virus for about one to three months after.
Especially when patients are up to date with coronavirus vaccinations, Arwady said there should not be "major concern" over contracting the virus soon again.
"At the beginning, we could very confidently, you know, sort of back in February, we could really confidently say that 90% of the people were not getting reinfected if they had COVID already," Arwady stated. "That's been dropping a little bit though around the world."
According to the Centers for Disease Control and Prevention, "after recovering from COVID, most individuals will have some protection from repeat infections."
"However, reinfections do occur after COVID-19," the CDC states, adding that changes and mutations "can lead to the emergence of variants that can increase the risk of reinfection."
Aside from being even more contagious than previous variants, scientists are tracking a mutation in BA.4 and BA.5 subvariants that could help it evade some immunity and cause reinfections.
A genetic trait that harkens back to the pandemic's past, known as a “delta mutation," appears to allow the BA.2.12.1 subvariant "to escape pre-existing immunity from vaccination and prior infection, especially if you were infected in the omicron wave," said Dr. Wesley Long, a pathologist at Houston Methodist in Texas. That's because the original omicron strain that swept the world didn’t have the mutation.
The genetic change is also present in the omicron relatives BA.4 and BA.5. Those have exactly the same mutation as delta, while BA.2.12.1 has one that's nearly identical.
This genetic change is bad news for people who caught the original omicron and thought that made them unlikely to get COVID again soon.
Although most people don't know for sure which variant caused their illness, the original omicron caused a giant wave of cases late last year and early this year.
Long said lab data suggests a prior infection with the original omicron is not very protective against reinfection with the new mutants, though the true risk of being reinfected no matter the variant is unique to every person and situation.
According to the latest data, those sickened by delta previously may have some extra armor to ward off the new mutants. A study released before it was reviewed by other scientists, by researchers at Ohio State University, found that COVID patients in intensive care with delta infections induced antibodies that were better at neutralizing the new mutants than patients who caught the original omicron.
“The omicron infection antibody does not appear to protect well against the subvariants compared to delta,” said Dr. Shan-Lu Liu, a study author who co-directs the viruses and emerging pathogens program at Ohio State.
But Liu said the level of protection a delta infection provides depends partly on how long ago someone was ill. That's because immunity wanes over time.
People who got sick with delta shouldn’t think of themselves as invulnerable to the new subvariants, especially if they’re unvaccinated, Long said. “I wouldn’t say anyone is safe."