The question of how protected someone is from COVID infection has received varying answers since the start of the pandemic, but as the super-contagious omicron subvariants dominate cases in the United States, they could mark a another change.
Chicago’s Top Physician noted that while the omicron variant itself marked a distinct shift in reinfections, eschewing natural immunity against infection by previous strains, BA.5 also evaded immunity against even other omicron infections.
“All the variants before that, we weren’t seeing a lot of reinfection with the current variant,” said Dr. Allison Arwady, commissioner of the Chicago Department of Public Health. “So we saw people who had alpha or delta in the past being relatively protected, but potentially infected with omicron. Everything has been omicron since January, to be clear – all of these subvariants are different versions of omicron. BA .4, BA.5 is the first where we see re-infection even of people who had an earlier version of omicron, so it’s different.
Arwady said while it’s still not common to get re-infected if you’ve recently had COVID, “we’re seeing more of these infections.”
“Especially if you’re counting on an omicron infection from six months ago, don’t count on it,” she said.
In addition to being even more contagious than previous variants, scientists have tracked a mutation in BA.4 and BA.5 that may help it evade some immunity and cause reinfections.
A genetic trait reminiscent of the pandemic past, similar to the so-called “delta mutation”, appears to allow subvariants “to escape pre-existing immunity from vaccination and prior infection, especially if you’ve been infected with the omicron wave,” said Dr. Wesley Long, pathologist at Houston Methodist in Texas. This is because the original strain of omicron that swept the world didn’t have the mutation.
This genetic change is bad news for people who caught the original omicron and thought it made them unlikely to get COVID-19 again soon. Although most people aren’t sure which variant caused their disease, the original omicron caused a giant surge of cases late last year and early this year.
Long lab data suggests that prior infection with the original omicron is not very protective against reinfection with the new mutants, although the true risk of being reinfected, regardless of variant, is unique to each person and each situation.
However, vaccinations against COVID-19 continued to prevent serious hospitalizations and deaths, Arwady said.
Two new omicron subvariants known as BA.4 and BA.5 are gaining traction in the United States, but how transmissible are they and what do we know about them?