Vaccine campaigns will likely have to continue for many years as the Covid immunity induced by the shots is ‘highly likely to wane over time’, according to scientific advisers to the government.
“It is highly likely that vaccine induced immunity to SARS-CoV-2 infection, and potentially
severe disease (but probably to a lesser extent) will wane over time,” the scientists said in a report summary for the government’s Scientific Advisory Group for Emergencies (SAGE).
Compromised immunity would most likely be first detected among vulnerable groups in the population, the scientists said, manifesting in hospitalisations due to infection.
“It is therefore likely that there will be vaccination campaigns against SARS-CoV-2 for many years to come, but currently we do not know what will be the optimal required frequency for re-vaccination to protect the vulnerable from COVID disease,” the summary continued.
In the UK, groups of the population have been vaccinated with three main vaccines since the rollout began in December 2020: AstraZeneca, Pfizer/BioNTech, and Moderna.
Amongst adults under 30, who were last to be offered the vaccine, the main vaccine currently being administered is Pfizer, due to a rare blood clot risk in younger receptors of the AstraZeneca jab.
It comes as Pfizer published notes in its second-quarter earnings report about a study of 45,000 people worldwide, which has not yet been peer-reviewed, that suggested a gradual “declining trend in vaccine efficacy” over the six months after two doses of its vaccine.
Echoing the SAGE adviser’s projections, the Pfizer study showed that the vaccine continued to offer strong protection against hospitalisation and more serious manifestations of the disease after six months, but overall protection appeared to weaken.
The SAGE advisers also said that immunity endurance may differ, dependent on the vaccine administered.
“Different vaccines may induce different sorts of immunity, which may have different duration. Absolute correlates of protection are yet to be determined, but the only ready measure that can be used at scale is of serum antibody,” the report said.
The scientists’ findings will boost the argument for booster shots over time as new variants emerge, a month after researchers at Oxford University found that a third “booster” shot of the AstraZeneca vaccine gave the best protection against the virus.