Timing of last COVID-19 vaccine dose and SARS-CoV-2 breakthrough infections in fully (boosted) vaccinated healthcare personnel.

AIM: To estimate the incidence, timing, and severity of SARS-CoV-2 breakthrough infections in fully vaccinated healthcare personnel (HCP). METHODS: We prospectively studied 6496 fully vaccinated HCP from November 15, 2021 through April 17, 2022. Full COVID-19 vaccination was defined as a complete primary vaccination series followed by a booster dose at least six months later. RESULTS: A total of 1845 SARS-CoV-2 breakthrough infections occurred (28.4 episodes per 100 HCP), of which 1493 (80.9%) were COVID-19 cases and 352 (19.1%) were asymptomatic infections. Of the 1493 HCP with COVID-19, 4 were hospitalized for 3-6 days (hospitalization rate among HCP with COVID-19: 0.3%). No intubation or death occurred. SARS-CoV-2 breakthrough infections occurred at a mean of 16.2 weeks after the last vaccine dose. Multivariable regression analyses showed that among the 1845 HCP with a breakthrough infection, the administration of a COVID-19 vaccine dose >16.2 weeks before the infection was associated with an increased likelihood in developing COVID-19 rather than asymptomatic SARS-CoV-2 infection (OR: 1.58; 95% CI: 1.01-2.46; p-value=0.045) compared to administering a vaccine dose later. The likelihood of developing COVID-19 versus asymptomatic infection increased by 7% weekly after the last COVID-19 vaccine dose (OR: 1.07; 95% CI: 1.03-1.11; p-value=0.001). CONCLUSION: SARS-CoV-2 breakthrough infections are common among fully (boosted) vaccinated HCP. However, full COVID-19 vaccination offered considerable protection against hospitalization. Our findings may contribute to defining the optimal timing for booster vaccinations. More efficient COVID-19 vaccines that will also confer protection against SARS-CoV-2 infection are urgently needed.

Association between COVID-19 vaccination status, time elapsed since the last vaccine dose, morbidity, and absenteeism among healthcare personnel: A prospective, multicenter study.

AIM: We assessed the impact of COVID-19 vaccination status and time elapsed since the last vaccine dose on morbidity and absenteeism among healthcare personnel (HCP) in the context of a mandatory vaccination policy. METHODS: We followed 7592 HCP from November 15, 2021 through April 17, 2022. Full COVID-19 vaccination was defined as a primary vaccination series plus a booster dose at least six months later. RESULTS: There were 6496 (85.6 %) fully vaccinated, 953 (12.5 %) not fully vaccinated, and 143 (1.9 %) unvaccinated HCP. A total of 2182 absenteeism episodes occurred. Of 2088 absenteeism episodes among vaccinated HCP with known vaccination status, 1971 (94.4 %) concerned fully vaccinated and 117 (5.6 %) not fully vaccinated. Fully vaccinated HCP had 1.6 fewer days of absence compared to those not fully vaccinated (8.1 versus 9.7; p-value < 0.001). Multivariable regression analyses showed that full vaccination was associated with shorter absenteeism compared to not full vaccination (OR: 0.56; 95 % CI: 0.36-0.87; p-value = 0.01). Compared to a history of ≤ 17.1 weeks since the last dose, a history of > 17.1 weeks since the last dose was associated with longer absenteeism (OR: 1.22, 95 % CI:1.02-1.46; p-value = 0.026) and increased risk for febrile episode (OR: 1.33; 95 % CI: 1.09-1.63; p-value = 0.004), influenza-like illness (OR: 1.53, 95 % CI: 1.02-2.30; p-value = 0.038), and COVID-19 (OR: 1.72; 95 % CI: 1.24-2.39; p-value = 0.001). CONCLUSIONS: The COVID-19 pandemic continues to impose a considerable impact on HCP. The administration of a vaccine dose in less than four months before significantly protected against COVID-19 and absenteeism duration, irrespective of COVID-19 vaccination status. Defining the optimal timing of boosters is imperative.

COVID-19 vaccination significantly reduces morbidity and absenteeism among healthcare personnel: A prospective multicenter study.

AIM: Healthcare personnel (HCP) are prioritized for coronavirus disease 2019 (COVID-19) vaccination to protect them and non-disruptive provision of healthcare services. We assessed the impact of the Pfizer-BioNTech vaccine on morbidity and absenteeism among HCP. METHODS: We studied 7445 HCP in five tertiary-care hospitals in Greece from November 15, 2020 through April 18, 2021. RESULTS: A total of 910 episodes of absenteeism and 9695 days of absence were recorded during the entire study period. Starting from January 4, 2021, 4823/7445 HCP (64.8%) were fully or partially vaccinated. Overall, 535 episodes of absenteeism occurred from January 4, 2021 through April 18, 2021, including 309 (57.76%) episodes among 2622 unvaccinated HCP and 226 (42.24%) episodes among 4823 vaccinated HCP (11.8 versus 4.7 episodes of absenteeism per 100 HCP, respectively; p-value < 0.001). The mean duration of absenteeism was 11.9 days among unvaccinated HCP compared with 6.9 days among vaccinated HCP (p-value < 0.001). Unvaccinated HCP more frequently developed acute respiratory infection, influenza-like illness, and COVID-19 (p-values < 0.001 for all comparisons). Vaccine effectiveness for fully vaccinated HCP was estimated at 94.16% [confidence interval (CI): 88.50%-98.05%) against COVID-19, 83.62% (CI: 73.36%-90.38%) against SARS-CoV-2 infection (asymptomatic or COVID-19), and 66.42% (CI: 56.86%-74.15%) against absenteeism. CONCLUSION: The COVID-19 pandemic had a considerable impact on healthcare workforce. The Pfizer-BioNTech vaccine significantly reduced morbidity, COVID-19, absenteeism and duration of absenteeism among HCP during a period of high SARS-CoV-2 circulation in the community. It is expected that HCP vaccination will protect them and healthcare services and contain healthcare costs.