Previous Omicron infection protects against BA.4 and BA.5 . variants


People queued at a COVID-19 testing site in New York City last month, when the BA.4 and BA.5 subvariables were taking hold.Credit: John Smith/View Press/Getty

The Omicron BA.4 and BA.5 sub variants of SARS-CoV-2 have been shown to be more stealthy in evading the immune defenses of people of all their ancestors.

But recent research shows that previous infection with an older variant (such as Alpha, Beta, or Delta) offers some protection against reinfection with BA.4 or BA.5, and that previous Omicron infection is significantly more effective. This was the result of a study that evaluated all cases of novel coronavirus infection in Qatar since the start of the wave of infection with BA.4 and BA.5 (BA.5).1.

The work, which was published on the preprint server medRxiv on July 12 and has not yet been peer-reviewed, feeds into broader research on “how to integrate different immunity into one another,” says study co-author Laith Abu-Raddad, an infectious-disease epidemiologist. at Weill Cornell Medicine – Qatar in Doha.

Everyone has a different immune history, because people have received different combinations of COVID-19 vaccines and have been infected with different types of vaccines during the course of the pandemic. “Different dates provide people with different immunity to the next infection,” says Abu-Raddad. He adds that knowing how these diverse immune responses interact within a person will be “very important for the future of the epidemic.”

natural immunity

To see how much protection a previous infection affords against two Omicron sub-variants, Abu-Raddad and colleagues analyzed COVID-19 cases recorded in Qatar between May 7 of this year—when BA.4 and BA.5 first entered the country—and July 4. They looked at the number of people known to have been previously infected who tested positive for COVID-19, and determined which infection was caused by BA.4 or BA.5 by screening positive test samples to see if they contained a protein that these subvariants lacked.

The researchers found that infection with the pre-Omicron variant prevented re-infection with BA.4 or BA.5 with an effectiveness of 28.3%, and also prevented recurrence of symptoms with any of the subvariants with an effectiveness of 15.1%. Previous infection with Omicron gave stronger protection: it was 79.7% effective in preventing re-infection with BA.4 and BA.5 and 76.1% effective in preventing recurrence of symptoms.

Although it seems inconsequential that we would see stronger protection against any infection again than the return of symptomatic infection, the researchers say that this effect is in line with previous studies and may be due to estimates that have wide confidence intervals.

time between infection

“It’s a good study,” says Kei Sato, a virologist at the University of Tokyo. But he notes that the length of time between the first and second infection could have affected the results. Previous variants were longer than the Omicron, which only appeared in late 2021. Several studies, including one by the same team in Qatar2showed that the natural immunity to SARS-CoV-2 diminishes over time.

Alex Segal, a virologist at the African Health Research Institute in Durban, South Africa, agrees. “The time that [has] It passed because the original infection was much shorter with Omicron, so it’s not a fair comparison,” he says. Segal adds that participants’ vaccination statuses are unclear from the results, as well as information about whether the primary infection occurred before or after vaccination, which could to be an important consideration.

Abu-Raddad says the purpose of the study is to check on people who are currently more susceptible to reinfection, rather than attributing natural immunity to a particular viral strain. He says the study design controls for vaccination effects, and the team performed a sensitivity analysis to adjust for vaccine status, and its results were consistent with the overall conclusions.

“The immunity you get from this omicron infection actually protects you from other omicron subspecies to some extent,” Segal says. However, Sato warns, “Covid is everywhere.” “It could easily evolve into a new variant.”

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