The body's natural immune response following COVID infection is sustained for up to seven months, but these antibodies are not sufficient against contemporary variants of the virus, finds a study suggesting the importance of vaccines against the infectious disease.

The study, published in the PLOS Medicine, also stressed the need to invest in new vaccine designs to keep pace with emerging COVID variants.

Researchers analysed the serum of 233 individuals diagnosed with COVID-19 over seven months and found that the level of immunity over time is dependent on disease severity and the viral variant.

Further, the antibodies developed during the first wave also had reduced effectiveness against six variants, ranging from those observed in the second wave in Australia through to three variants of concern that have driven the global pandemic in the UK, Brazil, and South Africa.

"We can learn a great deal from these people who were infected in the first wave in Australia as they were infected with the same variant that our current vaccines are based on," said Fabienne Brilot, Associate Professor at the University of Sydney.

"While the approved vaccines are showing good responses, our study highlights the importance of continued vaccine development, especially taking into account the differences in variants," Brilot added.

The study was conducted to investigate the level, breadth, and longevity of the immunity generated from COVID-19 infection and whether mutation of the virus compromises immunity.

The team examined the effect of 10 COVID-19 strains and variants of concern/interest including the first known classified SARS-CoV-2 strain (D614), Alpha (B117), Beta (B1351), Gamma (P1), and Zeta (P2).