Even as new subvariants of omicron emerge, COVID-19 is becoming a seasonal illness with predictable surges in summer and winter, says Shangxin Yang, PhD, a clinical microbiologist at UCLA Health.
Omicron variants BA.4 and BA.5 are causing a spike in cases in South Africa, where it’s winter, continuing a pattern of semi-annual COVID-19 surges there.
The genetic makeup of these variants — which allows them to evade immunity from previous infection — and the timing of their emergence in the Southern Hemisphere point to a surge in the United States in the coming months, Dr. Yang says.
Antibodies against the virus produced through vaccination or previous infection naturally wane after about four months. Given that California’s last case surge was in December and January, “a lot of people are losing that antibody level to the point that they are susceptible to be reinfected,” Dr. Yang says.
“Combining the timing with the genetic characteristics of BA.4 and BA.5, we might expect there’s going to be another surge coming in the summer,” he says. “Usually we are about a month or so behind what’s found in South Africa.”
Evidence points to this seasonal pattern becoming something of a new normal with COVID-19.
Over the past two years, we’ve seen a surge in winter, as people gather indoors and travel for the holidays. Then, six months later, as antibodies wane and the summer travel season begins, there’s another rise in cases.
“In Southern California and the L.A. area, we’ve been seeing this pattern — in summer, you have a small surge and winter you have a big surge,” Dr. Yang says.
Reinfection more likely among unvaccinated
Unvaccinated people continue to be most vulnerable to infection and reinfection with the new omicron variants, according to a new study.
It’s a good reason to get vaccinated or boosted now, Dr. Yang says.
COVID-19 may no longer present a serious threat to the general population, most of whom have been vaccinated or previously infected, but high-risk individuals remain vulnerable to this ever-evolving virus, he says.
It's seasonal
It may be that BA.4 and BA.5 have evolved to the point that they are no longer variants of omicron, but a distinct new “variant of concern.” That’s up to the World Health Organization to determine, Dr. Yang says. The WHO identifies a “variant of concern” as one more likely to cause breakthrough infections or reinfections, or increase in virulence or change in clinical disease presentation.
Either way, the global population has to remain flexible and responsive, he says, as new coronavirus variants continue to emerge.
“We’re going to live with the virus forever and we’re going to have to deal with it,” he says. “When the activity is low, we can enjoy life. When the activity is high, or the concern is definitely there, we just have to be more cautious.”
That means that when viral circulation is high, it’s probably wise to wear a mask in crowded situations — particularly if you spend time with people with compromised immune systems or other vulnerabilities to severe disease from COVID-19.
Luckily, the original vaccines appear to provide protection against serious illness even as the virus mutates. Dr. Yang anticipates that we may ultimately need booster shots twice a year, unlike the once-annual flu vaccine.
Getting a shot every six months would protect against the now-predictable seasonal surges, he says.
“It’s a pretty clear pattern that we have two surges a year, so it’s seasonal,” Dr. Yang says. “That’s what we want, right? It’s not a pandemic. It’s endemic.”
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