Booster shots that use different technologies than the first two doses could improve vaccine-induced immune protection against the highly transmissible Omicron variant of the coronavirus, a new study by Chinese researchers suggested.

A third heterologous protein subunit vaccine following two doses of inactivated vaccines could provide better protection against Omicron than using the latter as a booster shot, according to the paper published Wednesday by the National Medical Center for Infectious Diseases at Shanghai’s Huashan Hospital of Fudan University. The study is China’s first peer-reviewed paper on the effectiveness of vaccine boosters against Omicron.

Researchers suggested that Omicron is more likely to evade immunity than other COVID-19 strains, adding that a third shot — either using the same technology or a mix and match approach — could protect against severe disease and mortality caused by the variant.

“Vaccine boosters can enhance the immune barrier, but cannot completely stop the spread of Omicron,” researchers said in a separate article Thursday. “Currently, the best strategy to form an immune barrier against Omicron worldwide is to intensify public health and social measures and get a third booster shot.”

The study echoes research results from the United Kingdom and Hong Kong that suggested Omicron can escape immune response from a double-dose regimen, while a booster shot can increase protection against it.

Since it was first detected in November, the Omicron variant has “raised serious concerns due to multiple mutations, reported significant immune escape, and unprecedented rapid spreading speed,” Wednesday’s study said. The variant has now spread to at least 106 countries and regions, with at least seven cases detected in the Chinese mainland as of Saturday.

Meanwhile, international studies have recently found Omicron cases are less likely to result in hospitalizations compared with the Delta variant, while scientists have warned the severity of the new variant is not yet fully understood.

With China detecting several Omicron cases amid prolonged waves of infections, cities across the country are urging residents to get boosted using the same type of vaccine previously administered. Authorities haven’t yet greenlighted mixing and matching COVID-19 vaccines, though there have been signals that China may introduce booster shots with different technical routes to enhance immunity.

“It remains to be seen whether the mix-and-match approach can be supported by more data,” an immunologist from a leading Chinese university, who requested anonymity as he is not authorized to speak to the media, told Sixth Tone. “Mixing vaccines would increase the kinds of vaccine ingredients we are exposed to, adding to safety concerns.”

Editor: Bibek Bhandari.

(Header image: alvarez/E+/People Visual)