Effects of return-to-office, public schools reopening, and vaccination mandates on COVID-19 cases among municipal employee residents of New York City (preprint)

ObjectiveOn September 13, 2021, teleworking ended for New York City municipal employees, and Department of Education (DOE) employees returned to reopened schools. On October 29, COVID-19 vaccination was mandated. We assessed these mandates short-term effects on disease transmission. MethodsUsing difference-in-difference analyses, we calculated COVID-19 incidence rate ratios (IRR) among residents 18-64 years-old by employment status pre- and post-policy implementation. ResultsIRRs post-(September 23-October 28) vs. pre-(July 5-September 12) return-to-office were similar between office-based City employees and non-City employees. Among DOE employees, the IRR after schools reopened was elevated 28.4% (95% CI: 17.3%-40.3%). Among City employees, the IRR post-(October 29-November 30) vs. pre- (September 23- October 28) vaccination mandate was lowered 20.1% (95% CI: 13.7%-26.0%). ConclusionsWorkforce mandates influenced disease transmission, among other societal effects.

Reduced Odds of SARS-CoV-2 Reinfection after Vaccination among New York City Adults, June-August 2021 (preprint)

BackgroundBelief in immunity from prior infection and concern that vaccines might not protect against new variants are contributors to vaccine hesitancy. We assessed effectiveness of full and partial COVID-19 vaccination against reinfection when Delta was the predominant variant in New York City. MethodsWe conducted a case-control study in which case-patients with reinfection during June 15- August 31, 2021 and control subjects with no reinfection were matched (1:3) on age, sex, timing of initial positive test in 2020, and neighborhood poverty level. Conditional logistic regression was used to calculate matched odds ratios (mOR) and 95% confidence intervals (CI). ResultsOf 349,598 adult residents who tested positive for SARS-CoV-2 infection in 2020, did not test positive again >90 days after initial positive test through June 15, 2021, and did not die before June 15, 2021, 1,067 were reinfected during June 15-August 31, 2021. Of 1,048 with complete matching criteria data, 499 (47.6%) were known to be symptomatic for COVID-19-like-illness, and 75 (7.2%) were hospitalized. Unvaccinated individuals, compared with fully vaccinated individuals, had elevated odds of reinfection (mOR, 2.23; 95% CI, 1.90, 2.61), of symptomatic reinfection (mOR, 2.17; 95% CI, 1.72, 2.74), and of reinfection with hospitalization (mOR, 2.59; 95% CI, 1.43, 4.69). Partially versus fully vaccinated individuals had 1.58 (95% CI: 1.22, 2.06) times the odds of reinfection. All three vaccines authorized or approved for use in the U.S. were similarly effective. ConclusionAmong adults with previous SARS-CoV-2 infection, vaccination reduced odds of reinfections when the Delta variant predominated.

Reduced COVID-19 Hospitalizations among New York City Residents Following Age-Based SARS-CoV-2 Vaccine Eligibility: Evidence from a Regression Discontinuity Design (preprint)

Background: In clinical trials, several SARS-CoV-2 vaccines were shown to reduce risk of severe COVID-19 illness. Local, population-level, real-world evidence of vaccine effectiveness is accumulating. We assessed vaccine effectiveness for community-dwelling New York City (NYC) residents using a quasi-experimental, regression discontinuity design, leveraging a period (January 12-March 9, 2021) when [≥]65-year-olds were vaccine-eligible but younger persons, excluding essential workers, were not. Methods: We constructed segmented, negative binomial regression models of age-specific COVID-19 hospitalization rates among 45-84-year-old NYC residents during a post-vaccination program implementation period (February 21-April 17, 2021), with a discontinuity at age 65 years. The relationship between age and hospitalization rates in an unvaccinated population was incorporated using a pre-implementation period (December 20, 2020-February 13, 2021). We calculated the rate ratio (RR) and 95% confidence interval (CI) for the interaction between implementation period (pre or post) and age-based eligibility (45-64 or 65-84 years). Analyses were stratified by race/ethnicity and borough of residence. Similar analyses were conducted for COVID-19 deaths. Results: Hospitalization rates among 65-84-year-olds decreased from pre- to post-implementation periods (RR 0.85, 95% CI: 0.74-0.97), controlling for trends among 45-64-year-olds. Accordingly, an estimated 721 (95% CI: 126-1,241) hospitalizations were averted. Residents just above the eligibility threshold (65-66-year-olds) had lower hospitalization rates than those below (63-64-year-olds). Racial/ethnic groups and boroughs with higher vaccine coverage generally experienced greater reductions in RR point estimates. Uncertainty was greater for the decrease in COVID-19 death rates (RR 0.85, 95% CI: 0.66-1.10). Conclusion: The vaccination program in NYC reduced COVID-19 hospitalizations among the initially age-eligible [≥]65-year-old population by approximately 15%. The real-world evidence of vaccine effectiveness makes it more imperative to improve vaccine access and uptake to reduce inequities in COVID-19 outcomes.