The British government gambled correctly when it decided to extend the interval for booster vaccine doses to 12 weeks, according to a significant new analysis.
The delay in the booster has been shown to deliver a dramatic improvement in the efficacy of the Oxford adenoviral vaccine, according to a new analysis.
In a study yet to be peer-reviewed, the Oxford university researchers say that the single dose has also been found to have a significant effect on transmissibility.
According to their findings, a booster dose at less than six weeks delivers vaccine efficacy of 54.9% whilst after 12 weeks it increases it to 82.4%.
Meanwhile the first dose has protected 76% of patients from COVID-19 symptoms for up to 13 weeks, they report.
The research, from the monitoring of 17,000 people, is the latest counter-intuitive discovery about the adenoviral vaccine. At the outset researchers found that a reduced dose booster was more effective than a full dose.
The researchers found 332 cases of primary symptomatic disease.
They say that the first dose of the vaccine appears to achieve maximum protection after 22 days – and that there is little sign of it waning over 90 days.
Researcher Professor Andrew Pollard said: “These new data provide an important verification of the interim data that was used by more than 25 regulators including the MHRA and EMA to grant the vaccine emergency use authorisation.
“It also supports the policy recommendation made by the Joint Committee on Vaccination and Immunisation for a 12-week prime-boost interval, as they look for the optimal approach to roll out and reassures us that people are protected from 22 days after a single dose of the vaccine.”
* The Lancet reports evidence of the effectiveness of the Russian Sputnik vaccine, another adenoviral vaccine.
Analysis of 20,000 recipients found 91% efficacy – with 16 cases of infection reported among 15,000 vaccine recipients and another 62 cases among 4,900 people receiving a placebo.
Writing in the journal, commentators Professor Ian Jones, University of Reading, and Professor Polly Roy, London School of Hygiene & Tropical Medicine, UK, say: "The development of the Sputnik V vaccine has been criticised for unseemly haste, corner cutting, and an absence of transparency. But the outcome reported here is clear and the scientific principle of vaccination is demonstrated, which means another vaccine can now join the fight to reduce the incidence of COVID-19."
* A second study yesterday, examining a broad range of vaccines, suggests they are safe for children taking immunosuppressants for autoimmune diseases such as juvenile arthritis.
The Manchester University researchers studied the impact of flu, HPV, hepatitis, varicella, measles, mumps and rubella vaccines.
There was no major impact on immune responses from low dose steroids and biologics, they report in the Expert Reviews of Vaccines – although antibody concentrations were not always as high as in other vaccine recipients.
Researcher Dr Peter Arkwright said: “Though the prevention of infection is crucial in these patients, there have long been ongoing concerns from clinicians about the efficacy and safety of vaccination, particularly live-attenuated viral vaccines.
“The evidence shows that that both live and inactive vaccines are safe and effective and so hope this study will address those concerns. Children treated with immunosuppressive drugs for autoimmune diseases should receive vaccines to protect them from vaccine-preventable diseases.
“However, we do argue that patients taking high-dose steroids and pulse cyclophosphamide should avoid live viral vaccines.”
Single Dose Administration, And The Influence Of The Timing Of The Booster Dose On Immunogenicity and Efficacy Of ChAdOx1 nCoV-19 (AZD1222) Vaccine. Lancet preprint 2 February 2021
Lancet 2 February 2021
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