Vaccination alone unlikely to contain coronavirus in the UK, study warns

19 March 2021, 06:17

Vaccination alone is unlikely to contain coronavirus infections in the UK, but gradual reopening and high vaccine uptake could minimise future waves, new research suggests.

Vaccinating all adults in the UK is unlikely to achieve herd immunity and fully contain the virus, according to a new study.

Therefore, the gradual release of restrictions, high vaccine uptake, and a vaccine with high protection against infection is necessary to reduce the risk of future outbreaks, researchers say.

In England the road map out of lockdown, involves the slow and gradual relaxation of measures, with the majority of restrictions being eased after the most vulnerable have been vaccinated.

The modelling study was done before early real-world data from vaccination rollout studies.

Because preliminary findings suggest the vaccine offers some protection against infection, but the exact level is unknown, researchers analysed a range of levels of protection against infection.

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Professor Matt Keeling, from the University of Warwick, said: "Our modelling suggests that vaccination rollout in adults alone is unlikely to completely stop Covid-19 cases spreading 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.

"The huge success of the UK's vaccine programme so far coupled with the Government's gradual road map for easing restrictions are a cause for optimism.

"However, some measures, such as test, trace, and isolate, good hand hygiene, mask-wearing in high-risk settings, and tracing from super-spreader events, may also be necessary for some time."

Vaccination may offer a potential exit strategy for the pandemic and the UK currently ranks third globally for the total number of vaccine doses administered.

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The study published in Lancet Infectious Diseases modelled the combined vaccine rollout in the UK, 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% in those aged 80 years and older, 85% in those aged 50-79 years, and 75% in those aged 18-49 years.

It also looked at a more optimistic uptake scenario (95%, 90%, and 85%, respectively), and a more pessimistic scenario (90%, 80%, and 70%, respectively).

Last week Vaccines Minister Nadhim Zahawi told the Women and Equalities House of Commons Committee that an estimated 94% of the UK adult population had said they were likely or very likely to take up the coronavirus vaccine.

In the study, vaccine protection against symptomatic disease was assumed to be 88% based on phase three trial data from the Pfizer/BioNTech and Oxford/AstraZeneca vaccines being administered in the UK.

As vaccine protection against infection is still uncertain, it was varied in four scenarios (0%, 35%, 60%, and 85%).

The findings suggest that although vaccination can substantially reduce the R rate, it may not be enough to drive R below one without other control measures.

Under the most optimistic scenario for protection against infection (85%), researchers estimated R to be 1.58 without other controls.

According to the study, as vaccination alone is not expected to drive R below one, removing all restrictions after the vaccination rollout is complete is predicted to lead to another wave of infections with a substantial number of deaths.

It suggests that the scale of future waves and the number of deaths is influenced by how early and over what time-scales measures are relaxed, the vaccine's level of protection against infection, and vaccine uptake.

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The research found that a partial release in February 2021 was estimated to lead to 130,100 deaths by January 2024, whereas partial release in April 2021 lowers this to 61,400 deaths and partial release in June 2021 to 53,900 deaths.

If all control measures are removed in January 2022, after complete rollout of the vaccine, 21,400 Covid-19 deaths are estimated, if the vaccine prevents 85% of infection.

Partial release of control measures in February 2021 was predicted to lead to a wave of infection that peaks at 1,670 deaths per day.

But gradual release of measures over the course of five months or 10 months leads to waves that peak at 430 and 46 deaths per day, respectively.

Dr Sam Moore, from the University of Warwick, UK, said: "Since we conducted this study, new evidence suggests there may be a higher level of protection against severe disease offered by both the Pfizer/BioNTech and Oxford/AstraZeneca vaccines than the level we assumed.

"This may reduce the size of future hospital admissions and deaths we estimated, making future waves more manageable for the health service."

The authors note that their model does not account for the emergence of new variants, to which the vaccine might offer less protection, nor for the effects of waning immunity, which might necessitate additional vaccination.

They also say they were unable to look at the effects of relaxing individual control measures.