Some scientists fear that the future of Covid-19 may be the future of the virus that shows no signs of disappearing.

The coronaviruses has become more capable of reinfecting people. The newer versions of the Omicron variant, called BA.2 or BA2.12.1 in the United States, or BA.4 or BA.5 in South Africa, have already been reported as second infections by people with the first Omicron variant.

Researchers said in interviews that those people may have third or fourth infections within this year. Some people have long Covid symptoms that last for months or years.

Juliet Pulliam, an epidemiologist at Stellenbosch University in South Africa, said that it seems likely to be a long-term pattern.

There are going to be a lot of people getting infections.

It is difficult to quantify how often people are re-infecting each other. Dr. Pulliam and her colleagues have collected enough data in South Africa to say that the rate is higher with Omicron.

This isn't how it was supposed to be. Experts thought that immunity from vaccine would prevent most re infections.

Those hopes were dashed by the Omicron variant. Omicron and its descendants seem to have evolved to partially dodge immunity. Everyone is vulnerable to multiple infections, even those who have been vaccinations multiple times.

If we manage it the right way, most people will get it at least a couple of times a year.

The Covid vaccines have not been altered by the new variant. If a person tests positive for the coronaviruses, they won't need medical care, but they will be sick. A booster dose of the virus does seem to decrease the chance of re-infection, but not much.

Many experts believed that the coronaviruses would be similar to the flu. They predicted that there would be one big outbreak each year, most likely in the fall. The best way to stop its spread is to have a vaccine.

The coronavirus is behaving like four of its cousins, which cause colds throughout the year. Jeffrey Shaman, an epidemiologist at Columbia University in New York, said they saw people with multiple infections within a year while studying common-cold coronaviruses.

ImageClem Williams, 76, received a booster shot in Durham, N.C., this month.
Clem Williams, 76, received a booster shot in Durham, N.C., this month.Credit...Veasey Conway for The New York Times
Clem Williams, 76, received a booster shot in Durham, N.C., this month.

He said that the coronaviruses is not going to simply be this wintertime once-a-year thing.

Reinfections with earlier versions, including Delta, were relatively rare. The Omicron variant was identified in November and the pace of reinfections in South Africa seemed to pick up in September.

In the United States, there are many infections that have been reported, but in South Africa, there are many that have been reported.

The perception magnifies what is actually going on.

The Omicron variant was different from Delta and the other versions of the virus, so some reinfections were to be expected. New forms of Omicron seem to penetrate immune defenses with relatively few changes to its genetic code.

Alex Sigal is a researcher at the Africa Health Research Institute. It seems like you don't.

A weaker immune response is produced by an Omicron infections, compared to previous infections. Although the newer versions of the variant are closely related, they don't leave much protection against the others after three or four months.

The good news is that most people will not get sick from reinfecting with new versions of Omicron. The virus has not been able to completely sidestep the immune system.

It's probably as good as it gets for now, according to Dr. Sigal.

The constellation of symptoms known as Covid can last for months or years after an infection. It's too early to know how often an Omicron infection leads to long Covid, especially in vaccine recipients.

The Covid vaccine should be updated more quickly than the flu vaccine to keep up with the evolving virus. They said that even an imperfect match to a new form of the coronaviruses will still broaden immunity and offer some protection.

The virus tricks us every time we think we have the upper hand.