Coronavirus variants likely reinfecting Omicron survivors

A pair of new Omicron subvariants has emerged, raising the possibility that survivors of earlier Omicron strains can get reinfected.

BA.4 and BA.5 have gained increasing attention in South Africa as weekly coronavirus cases tripled in the last two weeks, according to data from Johns Hopkins University.

“It really came out of the blue over the weekend. We were already settling down with BA.2.12.1, and then BA.4 and BA.5?” said Dr. Peter Chin-hong, an infectious diseases expert at UC San Francisco. “It just seems like the latest chapter of a never-ending saga.”

The rapid growth of BA.4 and BA.5 in South Africa has implications for a potential future surge in California and the U.S. Until now, scientists had been reassured that people who survived the first Omicron variant over the winter, BA.1, were unlikely to be reinfected by the even more infectious subvariant BA.2, which is now dominant nationwide. But the surge in cases in South Africa of BA.4 and BA.5 follow an earlier Omicron wave. An estimated 90 per cent of South Africa’s population has immunity to the earlier Omicron variants either due to surviving a natural infection or through vaccination.

“If 90 per cent of people are immune already, and they’re seeing a surge in cases, it means that this particular dynamic duo [BA.4 and BA.5] are causing more reinfections — even in people who already had Omicron,” Chin-hong said.

Only a small number of cases of BA.4 and BA.5 have been documented in California. In April, one case of BA.5 was documented, and in March, one case of BA.4 was confirmed, according to the California Department of Public Health.