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BSI response to pre-print on the dosing schedule for the AstraZeneca/Oxford COVID-19 vaccine

2 February 2021

A new pre-print study from The Lancet provides data regarding the efficacy of the AstraZeneca/Oxford COVID-19 vaccine after extending the interval between the first and second doses.

In response, the British Society for Immunology has released the following statement:


Dr Doug Brown, Chief Executive of the British Society for Immunology, said:

“This new pre-print, currently under review at The Lancet, provides reassuring data regarding the dosing schedule for the AstraZeneca/Oxford COVID-19 vaccine. The team report that a longer gap of 3 months, compared with a gap of less than 6 weeks, between the first and second dose of the vaccine (such as that currently recommended in the UK) results in a vaccine efficacy of 82% after a second dose. These findings were backed up by analysis of antibody responses in people aged 18-55.  After one dose of the vaccine, researchers found a vaccine efficacy of 76% when measured up to 90 days post-vaccination before the second booster dose had been given. 

“This is positive news as it shows that just one dose of this vaccine generates good levels of immunity and that this protection does not seem to wane in the shorter term.  In immunology terms, this finding is not unexpected as we know that some other vaccines confer better immunity when the doses are more spread out.  Although further information is required to confirm these findings for older age groups, overall this new research should provide reassurance around the UK’s decision to offer the two doses of the vaccine 12 weeks apart.

“In addition to preventing people getting sick from COVID-19, the study also hints that the Oxford/AstraZeneca vaccine may be effective in stopping people being able to transmit the virus. While this would be extremely welcome news, we do need more data before this can be confirmed and so it’s important that we all still continue to follow social distancing guidance after we have been vaccinated.”

“While the results of this study show that a good level of immunity is still present at three months after one vaccine dose, it is important to remember that it is still the case that the highest and longest lasting protection from getting ill with COVID-19 will only be provided by getting two doses of the vaccine. In order to get this protection, it is critical that all people eligible for COVID vaccination do return to get their second dose when asked to do so by their medical providers.”


This paper is a pre-print reporting preliminary data that has not yet been peer-reviewed. You can read it here. Voysey et al. 2021 Single Dose Administration, And The Influence Of The Timing Of The Booster Dose On Immunogenicity and Efficacy Of ChAdOx1 nCoV-19 (AZD1222) Vaccine. SSRN: https://ssrn.com/abstract=3777268.