January 28, 2023

BA.5 causes more covid-19 reinfections, but doesn’t seem to increase their frequency, data reveal

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(CNN) — No, it’s not your imagination: As the BA.5 subvariant of the coronavirus spreads rapidly and sparks a spike in infections in the United States, more people are getting COVID-19 for a second or third time.

But, on average, these reinfections don’t seem to happen more often, according to a new analysis from Helix, a gene-sequencing company.

BA.5, a subvariant of omicron, currently causes about 80% of new covid-19 infections in the United States, according to latest data from the Centers for Disease Control and Prevention (CDC).

Helix, which sequences COVID-19 tests to monitor for variants, took a hard look at its data recently to learn how many times the same person has tested positive for COVID-19 and whether there are more reinfections now compared to previous waves of the pandemic.

BA.5 generates an increase in reinfections

Of the almost 300,000 infections registered since March 2021, the proportion corresponding to reinfections almost doubled from 3.6% during the wave of BA.2 last May to 6.4% during the wave of BA.5 in July .

However, it seems that these reinfections occur over longer periods than the last contagion.

In April, during the BA.2 surge, the average time between positive covid-19 tests for the same person was about 230 days. While in July it was about 270 days, about nine months.

“The most recent data we got showed that the fraction of all cases that were reinfections went up quite a bit. There was a jump,” said Shishi Luo, associate director of bioinformatics and infectious diseases at Helix.

New wave of covid-19 in the US with the BA.5 subvariant 2:05

Luo explained that he thinks a combination of factors — including decreased immunity, wide spread, and mutations in the BA.5 subvariant that help it evade the body’s defenses — likely contributed to the increase.

a lower frequency

On average, people who are currently suffering from reinfections were last infected about nine months ago. Now, that doesn’t mean there aren’t some recent cases where people had new episodes of covid-19 just a few weeks apart. Luo can detect them in the data. But they are not the norm.

“Statistically speaking, the more time that has passed since your last infection, based on the data we have generated, the more likely you are to be reinfected,” he said.

The Helix data agree with the results of a recent study about reinfection in Qatar, which routinely tests its 2.8 million residents for Covid-19, testing around 5% of the population each week.

The BA.4 and BA.5 sub-variants arrived in Qatar in May and by June they were already dominating transmission.

What can you do to stop the wave of covid infections? 3:28

The researchers used nationwide screening data to analyze reinfection cases.

protection against omicron

They found that people who were infected with covid-19 before the arrival of the omicron variant had very little protection against reinfection with symptoms during the BA.5 wave: just 15%. However, the protection from a past infection with an omicron variant was higher: around 76%.

“Those who got a pre-omcron variant now have really limited protection against BA.4 or BA.5 infection. So they really can’t count on natural immunity to protect them,” said Laith Abu- Raddad, an epidemiologist at Weill-Cornell Medicine-Qatar, in Doha, Qatar.

What is the reason for the rise in covid-19 infections in the US? 3:16

“Those who were most recently infected with an omicron variant have fairly good — but certainly not total — immunity against re-infection,” Abu-Raddad said.

The results of this study may not apply to everyone. Qatar’s population is unique in that it is made up mostly of men who travel to the country for work, the researchers say, and there are few people over the age of 50.

But Luo stressed that people should not panic when they learn that friends or relatives have contracted COVID-19 for the second time in a month. “That’s not the typical experience.”



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