But on average, those reinfections don’t seem to happen any faster, according to a new analysis from gene sequencing company Helix.
Helix, which sequences Covid-19 tests to monitor variants, recently probed its data to find out how many times the same person has tested positive for Covid-19 and whether there are more reinfections now compared to previous waves. .
Of nearly 300,000 infections since March 2021, the share of reinfections has almost doubled, from 3.6% in wave BA.2 in May to 6.4% in wave BA.5 in July.
These reinfections do not seem to be coming close, however.
In April, during the BA.2 wave, the average time between positive Covid-19 tests for the same person was around 230 days; in July it was about 270 days, or about nine months.
“The most recent data we had extracted showed that the fraction of all infections that are reinfections has increased significantly. There has been a jump,” said Shishi Luo, associate director of bioinformatics and infectious diseases at Helix.
Luo says she thinks a mix of factors — including waning immunity, wide spread, and BA.5 mutations that help it sneak past the body’s defenses — likely all contribute to the increase.
On average, people reinfecting themselves now were last infected about nine months ago. That doesn’t mean there aren’t recent cases in which people have had new bouts of Covid-19 within weeks of each other. Luo can see them in the data. But they are not the norm.
“Statistically speaking, you’re more likely to be reinfected the longer it’s been since your last infection, just based on the data we generated,” she said.
The BA.4 and BA.5 subvariants arrived in Qatar in May and dominated transmission by June.
Researchers used national testing data to examine cases of reinfection.
They found that people who had Covid-19 infections before the arrival of the Omicron variant had little protection against reinfection that caused symptoms during the BA.5 wave: only 15%. But protection against past infection with a variant of Omicron was higher: around 76%.
“Those infected with a pre-Omicron variant now have very limited protection against BA.4 or BA.5 infection, so they can’t really rely on natural immunity to protect them,” said Laith Abu-Raddad, epidemiologist at Weill-Cornell Medicine-Qatar, in Doha, Qatar.
“Those who were more recently infected with an Omicron variant have fairly good immunity – but of course not full immunity – against reinfection,” Abu-Raddad said.
These study results may not apply to everyone. Qatar’s population is unique because it is mostly made up of men who travel to the country for work, researchers say, and few people are over 50 years old.
But Luo says people shouldn’t panic when they hear of friends or family members contracting Covid-19 for the second time in a month. “Not the typical experience.”