Covid-19 vaccine boosters offer surprise defense

A breakthrough in immunology reveals current Covid-19 booster shots surprisingly offer some defense against future animal coronavirus outbreaks, while at the same time, evidence has emerged that the first infection in someone’s life imprints itself on the immune system and stays for years.

Both findings, published today in npj Vaccines and in iScience, shed light on the next generation of vaccine strategies and prepare the globe for future pandemics.

Key finding 1: Boosters offer hope against animal “spillover” threats

A team from the University of Cambridge Institute for Therapeutic Immunology & Infectious Disease (CITIID) analyzed the blood of older individuals who had been given four doses of a Covid-19 vaccine, including the bivalent Covid-19 booster shot.

The research revealed that the antibodies that the Covid-19 booster developed against newer, much more evolved human variants of Omicron have minimal power against these. Nevertheless, they proved effective in neutralising particular sarbecoviruses – a group of coronaviruses found in bats and pangolins that haven’t yet made the leap to humans.

“We were surprised to find that the vaccine provides protection against some animal coronaviruses with future pandemic potential,” said CITIID’s Dr Grace West, who is jointly first author of the npj Vaccines paper. “This could offer us some first line defense should there be an animal-to-human coronavirus spillover event and buy us time to develop appropriate therapies.”

Key finding 2: ‘Immune imprinting’ really is permanent

In parallel, researchers at CITIID collaborated with colleagues in Nigeria to study how sequences of viral exposure affect a person’s longer-term immune responses.

By studying individuals unvaccinated against Covid-19 and who had contracted the original strains naturally, they concluded the immune system “does not start again from zero” when confronted with a new variant or an updated vaccine. Rather, the first viral infection a person suffers imprints itself onto their immune system – or, ‘imprints’ the body’s first exposure.

In doing so the immune system becomes “predisposed to mount primarily the immune response against the initial infection when exposed to a novel or evolved variant of a virus or updated vaccine.”

This “immune imprinting” also explains why the Covid-19 booster provides significant defense against these particular bat and pangolin viruses. These sarbecoviruses have a very similar structure, with much less evolution of their spike protein compared to more recent human Covid variants, including Omicron, making them closely resemble the structure of the first virus we all encountered.

Shaping Next-Gen Vaccine Strategies

The dual findings underscore a shift in how future vaccines must be engineered. Rather than simply updating boosters to chase the latest human variant, global health leaders highlight the need for “pan-coronavirus” designs.

These next-generation shots aim to target shared, unmutated regions of the spike protein across multiple viral families, effectively overriding the constraints of immune imprinting while broadening defense against emerging wildlife threats.