New studies are emerging that suggest the latest version of the highly-infectious omicron variant is transmitting even faster than the original, and mild cases of the first may not offer much protection against future infections.

The findings cast doubt on hopes that the wave of omicron that’s sweeping the world may help hasten the end of the pandemic. Calls for governments to treat Covid-19 as endemic like influenza are rising globally as people grow tired of pandemic restrictions, vaccines become more accessible and deaths remain relatively low.

The production of neutralizing antibodies during an omicron infection appears related to the severity of the illness, according to one report from researchers at the University of California, San Francisco, that was published online before being peer-reviewed. The milder form of most omicron cases in vaccinated people may leave those who recover from them still vulnerable to existing virus and future variants that emerge, the researchers said.

The protection from a natural infection was about one-third that obtained through a booster shot, the study found.

“Our results suggest that omicron-induced immunity may not be sufficient to prevent infection from another, more pathogenic variant, should it emerge in the future,” the researchers said. “They also highlight the continued importance of vaccine boosters in enhancing immunity, as breakthrough infection alone may not be reliable” in protecting against repeat infections or future illness from new strains, they said.