key: cord-1038309-8uv8ol37
authors: Rhee, Chanu; Wang, Rui; Ye, Shangyuan; Baker, Meghan; Griesbach, Diane; Laskowski, Karl; Klompas, Michael
title: Decline in SARS-CoV-2 Infections Among Healthcare Workers at Two Hospitals Following Rollout and Administration of mRNA Vaccines
date: 2021-04-23
journal: Open Forum Infect Dis
DOI: 10.1093/ofid/ofab204
sha: 03874b2326d9b66cc39942af4add419c12d4c5a3
doc_id: 1038309
cord_uid: 8uv8ol37

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M a n u s c r i p t We compared weekly trends in HCW SARS-CoV-2 infections from October 5-January 31 to the 7-day average of new confirmed cases in Massachusetts 5 and the hospitals' 7-day average inpatient Covid-19 census. HCWs with any symptoms consistent with Covid-19 or unprotected exposures were required to undergo PCR testing; elective asymptomatic testing was also available at no cost. The hospitals'

Occupational Health Service interviewed all test-positive employees to assess symptoms and exposures. We compared trends in the pre-vaccine (October 5-January 3) vs post-vaccine period (January 4-31) by applying an interrupted time series model A c c e p t e d M a n u s c r i p t 3 to weekly case counts (log-transformed) and comparing slopes between HCWs, Massachusetts cases, and inpatient Covid-19 census. We used January 4th as the inflection point to allow adequate time for a meaningful fraction of HCWs to be vaccinated and because the trials suggested vaccine efficacy after about 2 weeks. 1, 2 Analyses were done using R version 4.0.3 (R Foundation).

Board. The need for written consent was waived as the data were collected for the purpose of hospital operations.

Between October 5-January 31, 1,004 HCWs tested positive for SARS-CoV-2

Weekly HCW infections increased from October through early January, closely mirroring trends in community and hospital cases ( Figure) . Of 23,329 HCWs, 7,542 (32%) received at least one vaccine dose by January 4 th , 12,438 (53%) by January 18 th , and 14,901 (64%) by January 31. After January 4th, there was a 33% weekly reduction in HCW infections from a peak of 116 to a low of 33 from January 25-31, while Massachusetts community cases and inpatient census declined more modestly (weekly 

Our study mirrors other data on the real-world impact of the mRNA vaccines, including in the general population in Israel, and HCWs in the United Kingdom and United States. [3] [4] [5] [6] [7] [8] Our analysis adds insight into the timeline after vaccine roll-out before which a substantial decline on infection rates is likely to be seen, and also underscores the fact that infections can still commonly happen within the first few weeks of vaccination and, occasionally thereafter, in fully vaccinated individuals as well.

Limitations of our study include the focus on two hospitals alone, incomplete vaccine uptake by staff, and insufficient time for all HCWs to receive two doses. The The proportion of HCWs vaccinated at various timepoints was as follows: 32% received 1 dose by January 4 th , 53% received 1 dose (10% received 2 doses) by January 18 th , and 64% received 1 dose (30% received 2 doses) by January 31 st .

A c c e p t e d M a n u s c r i p t 

Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine

Efficacy and Safety of the mRNA-1273 SARS-CoV-2 Vaccine

BNT162b2 mRNA Covid-19 Vaccine in a Nationwide Mass Vaccination Setting

Effectiveness of BNT162b2 mRNA Vaccine Against Infection and COVID-19 Vaccine Coverage in Healthcare Workers in England

Interim Estimates of Vaccine Effectiveness of BNT162b2 and mRNA-1273 COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among Health Care Personnel, First Responders, and Other Essential and Frontline Workers -Eight

Early Evidence of the Effect of SARS-CoV-2 Vaccine at One Medical Center

SARS-CoV-2 Infection after Vaccination in Health Care Workers in California

BNT162b2 mRNA Covid-19 Vaccine Effectiveness among Health Care Workers

Prevention (6U54CK000484-04-02).

Prevention, who are co-authors on this study, contributed to the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, and approval of the manuscript; and decision to submit the manuscript for publication.