Compared with the earlier Omicron BA.2 subvariant, currently dominant Omicron BA.5 is linked with higher odds of causing a second SARS-COV-2 infection regardless of vaccination status, a study from Portugal suggests.
From late April this year to early June, researchers studied 15,396 adults infected with the BA.2 variant and 12,306 infected with BA.5. The vaccines and boosters were equally effective against both sublineages, according to a report posted on medRxiv ahead of peer review.
However, 10% of BA.5 cases were reinfections, compared to 5.6% of BA.2 cases, which suggests a reduction in protection conferred by previous infection against BA.5 compared to BA.2, the researchers said. Moreover, the vaccines appeared to be less effective in reducing the risk of severe outcomes for BA.5 compared with BA.2.
