Vaccinations alone may not be enough to protect people with compromised immune systems from infection, even if the vaccine has generated the production of antibodies, new research from the University of Cambridge has shown.
The findings, published today in Science Advances, suggest that such individuals will need regular vaccine boosters to protect them and reduce the risk of infections that could be severe and also lead to new ‘variants of concern’ emerging.
Almost 16 million people worldwide are estimated to have died from Covid-19 during 2020 and 2021, though nearly 20 million deaths are thought to have been prevented as a result of the rapid rollout of vaccines against SARS-CoV-2, the virus that caused the pandemic.
During the pandemic, researchers discovered that immunocompromised individuals had difficulty clearing the virus, even when vaccinated. These are people whose immune systems are not functioning correctly, either as a direct result of disease or because they are on medication to dampen down their immune systems, for example to prevent organ transplant rejection. This meant that their infections lasted longer, giving the virus more opportunities to mutate.
Research from early in the pandemic showed that chronic infections can give rise to variants of concern that can then cause new waves of infection in the wider population.
When an individual is vaccinated, their immune systems produce antibodies that recognise and launch an attack on the virus. Such a process is known as seroconversion. Additional ‘booster’ vaccinations increase seroconversion and hence the likelihood of clearing infection.