Question to the Department of Health and Social Care:

To ask Her Majesty's Government what plans they have to collect evidence of the effectiveness of the second dose of the Pfizer/BioNTech COVID-19 vaccination being administered more than 21 days after the first.

Based on the data available to the Joint Committee on Vaccination and Immunisation the first dose of either Pfizer/BioNTech or Oxford/AstraZeneca vaccine provides substantial protection within two to three weeks of in particular for severe COVID-19 disease. The second vaccine dose is likely to be more important for duration and sustaining such protection. An appropriate dose interval may further increase vaccine efficacy. In the short term, the additional increase of vaccine efficacy from the second dose is likely to be modest as the great majority of the initial protection from clinical disease is after the first dose of vaccine.

Public Health England (PHE) is monitoring the effectiveness of the vaccines in the real world, including the effects of dosage schedules. Early data from PHE’s SIREN study shows a promising impact of vaccination on infection in healthcare workers aged under 65 years old.

Data shows one dose reduces the risk of catching infection by more than 70%, rising to 85% after the second dose of the Pfizer vaccine.