The elderly have been determined to be among those most vulnerable to coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The mortality rate and severity of the disease in this group are reported to be extremely high. In most countries, COVID-19 vaccination has been prioritized for residents and staff of long-term care facilities (LTCFs) and frontline workers. In Norway, residents of LTCFs primarily receive health care at the facility. They are generally not admitted to hospitals except in emergencies.
It is important to understand the vaccine effectiveness (VE) to determine how much protection it offers to the general population. Unfortunately, only a few studies are available that have determined the effect of the COVID-19 vaccine among the residents of LTCFs.
The unique setting in Norway allowed the scientists to study VE among both staff and residents in LTCFs.
Taking this opportunity, researchers focused on estimating the effectiveness of COVID-19 vaccines in preventing SARS-CoV-2 infections among residents and staff of LTCFs. They also analyzed the effect of the vaccine on the rate of hospitalization among staff and deaths among residents.
It must be highlighted that both these factors, i.e., mortality rate and hospitalization represent disease severity. This research, which can act as a guide for COVID-19 vaccination programs, is available on the medRxiv* preprint server.
Effectiveness of COVID-19 vaccines among residents and health care workers in LTCFs
In this study, researchers obtained data from BeredtC19, a preparedness registry containing individual-level data from various Norwegian registries.
They included all health care workers (HCW) who worked at LTCFs in the third week of January 2021 and residents who registered for a long-term stay at an LTCF in 2020.
This study excluded individuals who did not adhere to national recommendations about the interval between the first and second dose of the COVID-19 vaccine.
To avoid biases, individuals who had prior SARS-CoV-2 infection were not considered in this study. Researchers defined the vaccination status as unvaccinated (less than 14 days after the first dose of vaccine), partially vaccinated (14 days or more after the 1st dose and less than six days after the second dose), and fully vaccinated (seven days or more after the second dose).
In the sample considered for this study, 85.4% of LTCF residents and 71.1% of the HCWs received at least one vaccine dose during the follow-up period. The median ages of the residents and HCWs were estimated to be 87 years 39 years, respectively.
Researchers used Cox proportional hazard models to calculate VE in this study cohort, considering the vaccination status and adjusting for the age, sex, and associated underlying health conditions. They estimated the VE against positive SARS-CoV-2 infection to be 81.5% among the fully vaccinated and 40.8% for partly vaccinated residents and HCWs.
Scientists explained that in this study, personal attributes of LTCF residents, such as sex, age, and underlying conditions, had a minimal effect on the estimation result due to the relatively uniform population characteristics.
The Cox proportional hazard models could not estimate the degree of protection that prevailed among partly vaccinated residents, which may be due to rapid vaccination rollout and relatively short intervals between doses, i.e., residents received their second COVID-19 vaccine dose three weeks after the first.
The mortality rate of the resident population owing to COVID-19 disease was high. As a result, researchers estimated the VE in preventing death from COVID-19. They reported that in the fully vaccinated group, the mortality rate was reduced by 93.1%.
After adjusting for the age, sex, and underlying conditions of the HCWs, the VE against positive SARS-CoV-2 infection was estimated to be 45.0% among the partly vaccinated members and 81.4% among fully vaccinated candidates. Previous studies had reported a low mortality rate associated with COVID-19 in the general population of Norway.
Unlike the previous group, hospital admissions were considered to be an indicator of disease severity among HCWs. The current study reported that around 56 HCWs were hospitalized with COVID-19, among which two candidates were partly vaccinated.
None of the fully vaccinated HCW candidates required hospitalization. This study reported VE against COVID-19 hospitalization to be 81.7% for partly vaccinated HCWs in LTCFs.
Interestingly, this study observed that the total protection of unvaccinated residents significantly increased through staff vaccination. Thus, scientists believe that the outcomes of this study could be essential for the management of COVID-19 in LTCFs.
The current study reported a very high VE against SARS-CoV-2 infection and severe disease among residents and HCWs in LTCFs in Norway. The results of this study are in line with previous studies associated with high disease burden settings like LTCFs. The authors of this study have also highlighted the effectiveness of a single dose of vaccine in reducing hospital admissions among HCWs.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.