UK

Covid-19 vaccine programme 'not enough to achieve herd immunity'

The Oxford/AstraZeneca Covid-19 vaccine is being rolled out as part of a mass immunisation programme
The Oxford/AstraZeneca Covid-19 vaccine is being rolled out as part of a mass immunisation programme The Oxford/AstraZeneca Covid-19 vaccine is being rolled out as part of a mass immunisation programme

The British government's Covid-19 vaccination programme may not be sufficient to achieve herd immunity in the UK - especially when taking into account the highly transmissible new variant, scientists have warned.

Their findings, which have not been peer-reviewed, are based on a modelling study assessing the effectiveness of the UK-wide rollout of the Oxford/AstraZeneca and Pfizer/BioNTech vaccines.

Herd immunity can occur when most of the population becomes immune to an infectious disease such as Covid-19, thus providing indirect protection to those who are not immune.

Researchers from the University of East Anglia (UEA) said their results indicate that everyone, including children, would need to be inoculated with the "more effective" Pfizer jab in order for the UK to achieve herd immunity.

Coronavirus vaccines have not been licensed for use in children, but trials with young people are continuing.

The scientists recommend that all health and social care professionals should be vaccinated with either the Pfizer or Moderna jabs, both of which have reported around 95% efficacy in clinical trials, in order to prevent patients and vulnerable people from becoming infected with coronavirus.

Study author Professor Paul Hunter, from UEA's Norwich Medical School, said: "If we cannot achieve herd immunity, vulnerable unvaccinated individuals will remain at risk.

"We do need to consider how best to protect these individuals when social restrictions are eventually relaxed as the result of a successful vaccine rollout programme."

The researchers used mathematical modelling to assess how effective the Oxford and Pfizer vaccines would be in bringing the coronavirus reproduction number (R) down.

R is the number of people that one infected person, on average, will pass a virus on to.

When R is above 1, is means that the outbreak is growing.

Initial findings showed that 69% of the population would need to be given the Pfizer jab, or 93% the Oxford vaccine, to bring the R number below 1.

But when the researchers took into account the highly transmissible UK variant, they found that vaccinating the entire UK population with the Oxford jab would only reduce the R value to 1.3.

The Pfizer vaccine would require 82% of the population to be immunised to control the spread of the new variant, the researchers said.

But they pointed out that the Pfizer jab is not currently licensed for use on under-16s, who make up 19% of the population.

Professor Alastair Grant, form UEA's School of Environmental Sciences, and study co-author, said: "Also, some people will refuse the vaccine, so achieving an 82% vaccination rate (with the Pfizer vaccine) will likely be impossible."

He added: "The Oxford vaccine reduces the incidence of serious illness to a greater extent than it reduces symptomatic illness, which is still common in those who have had this vaccine.

"Its efficacy against the incidence of asymptomatic infections is lower, reducing its efficacy against all infection from 70.4% to 52.5% for the pooled data.

"This means that its overall protection against infection is only partial - around 50%."

Prof Grant said the combination of "relatively low headline efficacy and limited effect on asymptomatic infections" means the Oxford vaccine "cannot take us to herd immunity, even if the whole population is immunised".

He said: "For this reason, we recommend that health and social care workers, and others who have lots of contacts with those vulnerable to infection, should receive one of the mRNA vaccines in preference.

"The Oxford vaccine will no doubt be an important control intervention, but unless changes to the dose regime can increase its efficacy, it is unlikely to fully control the virus or take the UK population to herd immunity."

Commenting on the research, Professor Azra Ghani, chair in infectious disease epidemiology at Imperial College London, said the findings do not mean people will be living with the current level of Covid-19 restrictions indefinitely.

She said: "If a high proportion of those that are at risk of severe complications from the disease are vaccinated, then the number of hospitalisations and deaths will be dramatically reduced and the way we react to the circulating virus should become similar to the way that we react to other circulating viruses such as influenza.

"Furthermore, although the vaccines are not yet recommended for children, studies are under way and therefore it is likely that children could be vaccinated if that is considered necessary."