Pfizer-BioNTech mRNA BNT162b2 Covid-19 vaccine protection against variants of concern after one versus two doses

Abu-Raddad, L. J., Chemaitelly, H., Yassine, H. M., Benslimane, F. M., Al Khatib, H. A., Tang, P., Malek, J. A., Coyle, P., Ayoub, H. H., Al Kanaani, Z., Al Kuwari, E., Jeremijenko, A., Kaleeckal, A. H., Latif, A. N., Shaik, R. M., Abdul Rahim, H. F., Nasrallah, G. K., Al Kuwari, M. G., Al Romaihi, H. E., ... Bertollini, R. (2021). PfizerBioNTech mRNA BNT162b2 Covid-19 vaccine protection against variants of concern after one versus two doses. Journal of Travel Medicine, 28(7). https://doi.org/10.1093/jtm/taab083

Strategies for rolling out vaccination against Coronavirus Disease 2019 (Covid-19) varied across countries. A key question is whether delaying administration of the second vaccine dose to vaccinate the largest number of people in the shortest time, in situations of limited vaccine supplies and high incidence, could avert more disease cases, hospitalizations and deaths than the current protocol of a second dose shortly after the first dose.
BNT162b2 (Pfizer-BioNTech) vaccine effectiveness against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Qatar was recently reported with focus on individuals who completed 14 days after the second dose. 1 Here, we provide a follow-up analysis of how vaccine protection develops week-byweek after the first dose.
Data for SARS-CoV-2 were extracted from Qatar's nationwide digital-health information platform. The platform hosts the national centralized SARS-CoV-2 databases that captured all vaccination records, polymerase chain reaction (PCR) testing, and COVID-19 hospitalizations and deaths since epidemic start. 1 The study was conducted from 1 February to 31 March 2021, the period of rapid mass vaccination scale-up. Vaccine effectiveness was estimated using the test-negative case-control study design. 2 Cases and controls were matched one-to-one by age, sex,  Vaccine effectiveness was estimated using the test-negative, case-control study design. 2 Cases and controls were matched one-to-one by age, sex, nationality, and reason for PCR testing. Vaccine effectiveness is given by 2 Development of protection against infection and disease accelerated in the third week after the first dose, right before the second dose, reaching nearly 75% of the value attained ≥14 days after the second dose. Protection increased most rapidly against hospitalization and death and slowest against B.1.351 infection. While protection of one dose beyond 21 days could not be assessed, and existing protocol requires a second dose for optimal protection, these findings support the strategy of delaying the second dose to vaccinate the largest number of people in the shortest time, in situations of limited vaccine supplies and high incidence, given the substantial protection achieved after only one dose. In areas where B.1.351 is at high incidence, delivering the second vaccine dose at 3-6 weeks after the first dose may be considered with the lower and slower build-up of protection against this variant.

Key Points
• This population-based study documents BNT162b2 vaccine protection week-by-week after the first dose. • 75% of protection against infection and disease is reached 15-21 days after the first dose. • Protection increased most rapidly against hospitalization and death and slowest against B.1.351 infection. • While protection of one dose beyond 21 days could not be assessed, findings support delaying the second vaccine dose in situations of limited vaccine supplies and high incidence.

Authors' contributions
L.J.A. co-conceived and co-designed the study, led the statistical analyses, and co-wrote the first draft of the article. A.B. and R.B. co-conceived and co-designed the study. H.C. co-designed the study, performed the statistical analyses and co-wrote the first draft of the article. All authors contributed to data collection and acquisition, database development, discussion and interpretation of the results, and to the writing of the manuscript. All authors have read and approved the final manuscript.