How Often Can You Be Infected With the Coronavirus?
By Apoorva Mandavilli, May 16, 2022, NY Times

A virus that shows no signs of disappearing, variants
that are adept at dodging the body’s defenses, and waves
of infections two, maybe three times a year — this may be
the future of Covid-19, some scientists now fear.

The central problem is that the coronavirus has become
more adept at reinfecting people. Already, those infected
with the first Omicron variant are reporting second
infections with the newer versions of the variant — BA.2 or
BA2.12.1 in the United States, or BA.4 and BA.5 in South Africa.

Those people may go on to have third or fourth infections,
even within this year, researchers said in interviews. And
some small fraction may have symptoms that persist for months
or years, a condition known as long Covid.

“It seems likely to me that that’s going to sort of be a
long-term pattern,” said Juliet Pulliam, an epidemiologist
at Stellenbosch University in South Africa. “The virus is
going to keep evolving,” she added. “And there are probably
going to be a lot of people getting many, many reinfections
throughout their lives.”

It’s difficult to quantify how frequently people are reinfected,
in part because many infections are now going unreported.
Dr. Pulliam and her colleagues have collected enough data in
South Africa to say that the rate is higher with Omicron than
seen with previous variants.

This is not how it was supposed to be. Earlier in the pandemic,
experts thought that immunity from vaccination or previous
infection would forestall most reinfections. The Omicron
variant dashed those hopes. Unlike previous variants, Omicron
and its many descendants seem to have evolved to partially dodge
immunity. That leaves everyone — even those who have been
vaccinated multiple times — vulnerable to multiple infections.

“If we manage it the way that we manage it now, then most
people will get infected with it at least a couple of times a
year,” said Kristian Andersen, a virologist at the Scripps
Research Institute in San Diego. “I would be very surprised if
that’s not how it’s going to play out.”

The new variants have not altered the fundamental usefulness
of the Covid vaccines. Most people who have received three or
even just two doses will not become sick enough to need medical
care if they test positive for the coronavirus. And a booster
dose, like a previous bout with the virus, does seem to decrease
the chance of reinfection — but not by much.

At the pandemic’s outset, many experts based their expectations
of the coronavirus on influenza, the viral foe most familiar
to them. They predicted that, as with the flu, there might be
one big outbreak each year, most likely in the fall. The way to
minimize its spread would be to vaccinate people before its arrival.
Instead, the coronavirus is behaving more like four of its closely
related cousins, which circulate and cause colds year round. While
studying common-cold coronaviruses, “we saw people with multiple
infections within the space of a year,” said Jeffrey Shaman, an epidemiologist at Columbia University in New York.

If reinfection turns out to be the norm, the coronavirus is
“not going to simply be this wintertime once-a-year thing,” he
said, “and it’s not going to be a mild nuisance in terms of the
amount of morbidity and mortality it causes.”

Reinfections with earlier variants, including Delta, did occur
but were relatively infrequent. But in September, the pace of
reinfections in South Africa seemed to pick up and was markedly
high by November, when the Omicron variant was identified,
Dr. Pulliam said.

Reinfections in South Africa, as in the United States, may seem
even more noticeable because so many have been immunized or
infected at least once by now. “The perception magnifies
what’s actually going on biologically,” Dr. Pulliam said.
“It’s just that there are more people who are eligible for
reinfection.” The Omicron variant was different enough from
Delta, and Delta from earlier versions of the virus, that some
reinfections were to be expected. But now, Omicron seems to be
evolving new forms that penetrate immune defenses with relatively
few changes to its genetic code.

“This is actually for me a bit of a surprise,” said Alex Sigal,
a virologist at the Africa Health Research Institute. “I thought
we’ll need a kind of brand-new variant to escape from this one.
But in fact, it seems like you don’t.” An infection with Omicron
produces a weaker immune response, which seems to wane quickly,
compared with infections with previous variants. Although the
newer versions of the variant are closely related, they vary
enough from an immune perspective that infection with one doesn’t
leave much protection against the others — and certainly not after
three or four months.

Still, the good news is that most people who are reinfected with
new versions of Omicron will not become seriously ill. At least
at the moment, the virus has not hit upon a way to fully sidestep
the immune system. “That’s probably as good as it gets for now,”
Dr. Sigal said. “The big danger might come when the variant will
be completely different.” Each infection may bring with it the
possibility of long Covid, the constellation of symptoms that can
persist for months or years. It’s too early to know how often an
Omicron infection leads to long Covid, especially in vaccinated
people. To keep up with the evolving virus, other experts said,
the Covid vaccines should be updated more quickly, even more
quickly than flu vaccines are each year. Even an imperfect match
to a new form of the coronavirus will still broaden immunity and
offer some protection, they said. “Every single time we think we’re through this, every single time we think we have the upper hand, the
virus pulls a trick on us,” Dr. Andersen said. “The way to get it
under control is not, ‘Let’s all get infected a few times a year
and then hope for the best.’

https://www.nytimes.com/2022/05/16/health/covid-reinfection.html

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