COVID-19 Boosters Are Surprisingly Protective Against Animal Coronaviruses That Could Spark The Pandemics Of The Future

Some of these threats are complete unknowns, but there’s also a lot we can learn from the diseases that already affect us. COVID-19 is one example. SARS-CoV-2 was identified as new to us, but scientists had all their knowledge of other coronaviruses to draw on. 

One thing they didn’t have in 2020 was a pre-existing vaccine – but if history were to repeat itself, things could be very different.

New research led by scientists at the University of Cambridge with colleagues from across the world suggests that COVID-19 booster vaccines could offer some protection from future related coronaviruses that may spill over from animals into humans. 

“We may already have a head start when it comes to protecting against certain future outbreaks,” said co-first author Rebecca Morse from the Cambridge Institute of Therapeutic Immunology & Infectious Disease (CITIID) in a statement.

“Boosters could reduce both severity and spread if spillover were to occur, buying us vital time while we develop a more targeted vaccine.”

To reach their conclusion, the team looked at blood samples from UK adults who had received four COVID-19 vaccine doses, including a booster that targets both the original pandemic strain and the more recent Omicron variant. 

Antibodies from these blood samples were effective at neutralizing not only these strains of SARS-CoV-2, but other Omicron variants, the SARS-CoV-1 virus that caused the 2003 SARS epidemic, and similar viruses from bats and pangolins that have been tipped as future pandemic threats. 

The antibodies were actually most effective at neutralizing the bat and pangolin viruses, which was an unexpected result for the team – these viruses have never infected humans before.

This whole group of viruses, called the sarbecoviruses, has been the target of efforts to produce pan-coronavirus vaccines that are broadly protective against all of them. Recent notable studies include an experimental nanoparticle-based vaccine and the first-ever AI-designed vaccine, which just completed human trials. 

While these new findings will certainly help those designing the vaccines of the future, they also show that the vaccines we have right now have an important role to play. 

“We’d expect the COVID vaccine to offer protection against today’s variants, but we were surprised to find that it also provides protection against some animal coronaviruses with future pandemic potential,” said co-first author Grace West, also from CITIID.

The role of “imprinting”

Another recent paper from some of the same authors offers suggestions of why the current COVID-19 vaccines might produce such an unexpected response against animal coronaviruses. 

“The immune system doesn’t reset with each new variant. Instead, it builds on its first encounter, and that memory continues to influence how it responds to new variants,” explained first author Dr Adam Abdullahi of CITIID.

“It’s like how, when we have a negative encounter with someone the first time we meet, this first impression can be hard to shake and informs how we deal with them each time we meet.”

This phenomenon is called “immune imprinting”, and it occurs whether the first encounter with a particular virus is from a vaccine or a natural infection. 

In this study, the team sampled a population in Nigeria who had not had access to vaccines until 2023, most of whom had already been exposed to the COVID virus according to their bloodwork results. 

Over time, as pathogens mutate and new variants come along, there’s more chance they’ll stray far enough away from their original form to be able to escape our defenses. 

Essentially, this study suggests there’s a limit to what updating vaccines and giving booster doses can do about that, as any immune response is always somewhat shaped by that very first meeting between the virus and your body. 

“Understanding how populations were exposed to the virus is essential for designing effective vaccination strategies, particularly in settings where infection occurred before vaccine rollout,” said joint lead author Professor Alash’le Abimiku, from the Institute of Human Virology in Nigeria.

“Future vaccines may need to be designed so they don’t just ‘replay’ the immune system’s past experiences, but instead actively train it to recognise and respond well to new variants.”

Coming back to those bat and pangolin coronaviruses, they’re more similar to the original SARS-CoV-2 strain that emerged in late 2019 than they are to the currently circulating variants.

The idea of imprinting tells us that our immune responses are going to be most shaped by our first exposure to COVID. In the UK sample from the first study, it’s probable most of them either caught COVID before the vaccine rolled out, or else were vaccinated relatively early in 2021 against a pre-Omicron variant.

That could explain, then, why the antibodies from these quadruple-vaccinated people would still respond better to a virus that’s never been seen in humans, but that closely resembles the original SARS-CoV-2.

“Vaccines are still extremely important as they help reduce the severity of infection, so it’s important to get your boosters if you are vulnerable,” said Professor Ravindra Gupta, senior author of both papers. 

“But our findings help explain why we see different patterns of immunity across the world. The pandemic did not unfold uniformly, and our vaccination strategies need to reflect that reality.”

The papers are published in npj Vaccines and iScience.