London, March 19 : Vaccinating all adults in the UK is unlikely to achieve herd immunity and fully contain the virus, a new study suggests.
The modelling study, published in The Lancet Infectious Diseases journal, suggests that the gradual release of control measures, high vaccine uptake and a vaccine with high protection against infection is essential to minimise future waves of infection.
"Our modelling suggests that vaccination rollout in adults alone is unlikely to completely stop Covid-19 cases spreading in the UK," said researcher Matt Keeling, Professor at University of Warwick in the UK.
"We also found that early sudden release of restrictions is likely to lead to a large wave of infection, whereas gradually easing measures over a period of many months could reduce the peak of future waves," Keeling added.
This study modelled the combined interaction of the UK vaccination rollout with different scenarios of relaxing control measures, to predict the R number and deaths and hospital admissions due to Covid-19 from January 2021 to January 2024.
The model assumed vaccine uptake would be 95 per cent in those aged 80 years and older, 85 per cent in those aged 50-79 years, and 75 per cent in those aged 18-49 years, as well as looking at a more optimistic uptake scenario (95 per cent, 90 per cent, and 85 per cent, respectively), and a more pessimistic scenario (90 per cent, 80 per cent, and 70 per cent, respectively).
Vaccine protection against symptomatic disease was assumed to be 88 per cent based on phase 3 trial data from the Pfizer-BioNTech and Oxford-AstraZeneca vaccines being administered in the UK (the analysis was done before early real-world data from vaccination rollout studies).
Since the vaccines' protection against infection is still uncertain, it was varied in four scenarios (0 per cent, 35 per cent, 60 per cent, and 85 per cent).
The findings suggest that although vaccination can substantially reduce Reproduction (R), it may not be enough to drive R below 1 without other control measures. Under the most optimistic scenario for protection against infection (85 per cent), the R number is estimated to be 1.58 without other controls.