Jabs offer top protection against new strains over ‘natural’ immunity

An Australian study into the body’s immune response to Covid-19 has found that vaccination offers the best protection against the virus compared to the body’s response after becoming infected.

A health worker prepares the AstraZeneca Covid-19 coronavirus vaccine at a makeshift mass vaccination clinic in Denpasar, Indonesia. Picture: AFP

A study into the body’s immune response to Covid-19 has found that vaccination offers the best protection against the virus compared to the body’s response after becoming infected, with new variants proving more resistant to naturally acquired immunity.

The world-leading Australian study also found that some people who had recovered from Covid-19 became “super responders” with high levels of antibodies across all variants.

The team analysed blood samples, or serum, from 233 individuals who contracted the virus and found that the level of lasting immunity depended on the severity of illness and the variant involved.

It was also discovered that natural infection during the first wave offered little protection against newer variants, including the Alpha, Beta, Gamma and Zeta strains.

Sydney University Associate Professor and laboratory head at Kids Research at The Children’s Hospital at Westmead Fabienne Brilot, who was a co-author on the research, said that by tracking neutralising antibodies that bind to the virus her team was able to measure immunity.

“We looked at how many neutralising antibodies were generated and whether or not they could block further infections to assess and determine the neutralising antibody response,” she said.

“The antibody response in our blood lasts maybe for seven months and we also looked at if there is a large variation in how much antibodies are produced after natural infection.

“There were some people in our study who had just a few of those antibodies and some people who had a lot of them and we assessed whether or not they would be neutralising against the virus.”

Associate Professor Brilot said that the reason different people exhibited such diverse responses to the virus opened up the possibility of using blood plasma from more immune people in future treatments, though it was largely unclear why certain groups developed higher immunity.

“We don’t know why those people developed such a high immune response,” she said.

“In our study we saw that in general the people who got the most severe Covid-19 developed the largest immune response.

“Those super responders were really exceptional and the protection was broad enough to protect them against all the variants of concern.”

The Kirby Institute’s Stuart Turville, who was also a co-senior author of the paper, said the findings demonstrated the importance of the vaccine rollout for providing reliable protection.

“What this work has shown us is that vaccines offer a much broader protection against Covid-19 and its variants than the body’s natural immune response following infection, which is usually only protective against the variant of the virus that the person was infected with,” Associate Professor Turville said.

“We, therefore, should not rely on the body’s natural immune response to control this pandemic, but rather the broadly protective vaccines that are available.”

The study, which was published in PLOS Medicine, also involved collaboration between NSW Health Pathology and The Kirby Institute, which engineered cells to catch virus from swabs which were sequenced by the team at Prince of Wales Hospital.

Co-first author Fiona Tea, who took part in the research as part of her early postdoctoral fellowship, said the study provided unique insights into the nature of immunity as a result of contracting Covid-19.

“What makes this study stand out is the level and depth of analysis to neutralising antibody levels in people recovering from Covid infection over time, including comparison of infection recovering from different viral variants,” she said.