Nearly everyone who had a mild case of COVID-19 still has antibodies to the coronavirus a year later, but that might not protect them from new variants, a small study suggests.

Among 43 Australians who dealt with mild COVID-19 early in the pandemic, 90 per cent still had antibodies 12 months later. But only 51.2 per cent had antibodies that showed "neutralizing activity" against the original version of the virus and only 44.2 per cent had antibodies that could neutralize the early Alpha variant, the research team at the on medRxiv ahead of peer review.

Neutralizing antibodies against the now dominant and highly transmissible Delta variant were seen in only 16.2 per cent, with 11.6 per cent against Gamma, and against Beta in only 4.6 per cent.

Those who had mild COVID-19 "are vulnerable to infection with circulating and newly emerging SARS-CoV-2 variants 12 months after recovery," the researchers said.

The findings "reinforce the potential benefit" of tailoring vaccine boosters to currently circulating variants, similar to how annual flu vaccines are tailored to current influenza strains, they said.

(Reporting by Nancy Lapid; Editing by Bill Berkrot)