A phase three clinical trial study on the Pfizer-BioNTech COVID-19 vaccine efficacy demonstrated a two-dose vaccine efficacy of 95% with a second dose delivered between 19 and 42 days.

Using data available from this study, Public Health England estimated that short term vaccine efficacy from the first dose of the Pfizer-BioNTech vaccine to be approximately 89%. This is the efficacy calculated 15 to 21 days after the first dose. The estimate for 15 to 28 days is 91% which includes the seven days after the second dose and is prior to the time protection may be expected from the second dose.

There is no estimate of efficacy for a single dose beyond 21 days. Given the data available, evidence on the AstraZeneca COVID-19 vaccine and from the use of many other non-COVID-19 vaccines, the Joint Committee on Vaccination and Immunisation (JCVI) advises a maximum interval between the first and second doses of 12 weeks. The use of ‘short-term’ in this report refers to the impact of the programme over the first months of the programme. Further information on the estimates of efficacy of one dose is available in the JCVI’s statement on 31 December which is available at the following link:

https://www.gov.uk/government/publications/prioritising-the-first-covid-19-vaccine-dose-jcvi-statement/optimising-the-covid-19-vaccination-programme-for-maximum-short-term-impact

The British Medical Association have questioned the decision to use an extended schedule for COVID-19 vaccines. Data on the AstraZeneca vaccine indicate better immune responses from the second dose with an extended schedule and that protection is maintained over a twelve-week period.

The JCVI is of the view that the first dose of the Pfizer-BioNTech vaccine is likely to provide protection for at least 12 weeks.

There is no evidence to indicate a correlation between the presence of neutralising antibodies and a vaccine effect on transmission.

The JCVI aims to publish background documents to its meetings. However many of these relating to vaccine efficacy were provided to the committee in confidence or under a non-disclosure agreement and cannot be published by the JCVI. Evidence on vaccine immunogenicity and efficacy will be published by the relevant industry groups, usually in peer reviewed journals.