Question to the Department of Health and Social Care:

To ask Her Majesty's Government what evidence they have of the impact on the effectiveness of the Pfizer/BioNTech COVID-19 vaccination of postponing a second dose of the vaccination beyond 21 days from the first compared to giving such a dose within 21 days.

A phase three clinical trial study on COVID-19 vaccine efficacy demonstrated a two-dose vaccine efficacy of 95% with a second dose delivered between 19 and 42 days. A copy of the study Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine is attached.

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 Joint Committee on Vaccination and Immunisation’s view is that protective immunity from the first dose likely lasts for a duration of 12 weeks.