COVID-19 booster or additional primary vaccination dose against SARS-CoV-2 Omicron in nursing home occupants

By Shanet Susan AlexReviewed by Danielle Ellis, B.Sc.May 9 2022

A recent study posted to the Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report (MMWR) assessed the efficacy of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) primary series vaccination, additional initial dose, or booster shot against the SARS-CoV-2 Omicron infection in the nursing home.

Background

SARS-CoV-2-related morbidity and death are common among nursing home occupants. They were top-priority populations for early COVID-19 vaccination. Upon reports of reductions in CoV disease 2019 (COVID-19) vaccine-elicited immunity post-initial series immunization, i.e., two primary doses of a messenger ribonucleic acid (mRNA) vaccine (mRNA-1273 or BNT162b2) or one primary Ad26.COV2 vaccine shot, the CDC advised that all individuals aged 12 years or older should receive a SARS-CoV-2 booster vaccine dose. Moreover, an extra primary SARS-CoV-2 vaccination dosage is also advised for severely or moderately immunocompromised individuals, primarily consisting of many nursing home occupants. 

Nonetheless, there is scarce information about the vaccine efficacy (VE) of extra initial or booster SARS-CoV-2 vaccine doses against COVID-19 in the nursing home inhabitants, mainly against the highly transmissible SARS-CoV-2 Omicron variants.

About the study

In the present study, the researchers analyzed weekly SARS-CoV-2 vaccination coverage and surveillance data across nursing home residents provided to the National Healthcare Safety Network (NHSN) of CDC by skilled nursing facilities (SNFs) from February 14 to March 27, 2022. The SARS-CoV-2 Omicron variant was found in more than 99% of the sequenced isolates during the study period.

The authors aimed to determine comparative VE against COVID-19 for any SARS-CoV-2 booster or additional initial dose versus the primary series vaccination after controlling for the calendar week and variance across SNFs by assessing the SARS-CoV-2 vaccination and monitoring data from over 15,000 SNFs.

Each week, nursing facilities accredited by the Centers for Medicaid & Medicare Services (CMS) reported incident-confirmed COVID-19 among personnel and occupants to NHSN based on their vaccination status. Case data from CMS-certified SNFs was used in this investigation. Only close contacts of a SARS-CoV-2-infected resident or staff member were evaluated at SNFs with contact tracing capabilities. Infected people's vaccination status was divided into four categories: 1) main series alone, 2) booster or extra dose, 3) unvaccinated, and 4) other (unspecified vaccination or the receipt of one shot of mRNA vaccine).

Residents' weekly census by vaccination status was also reported weekly by SNFs. Further, the average of weekly resident numbers, by vaccination status, for each SNF was used to compute residents/weeks. The authors compared weekly COVID-19 cases accounting for vaccination status in each SNF to two weeks before weekly resident rates by vaccination status.

Results

According to study results, the comparative VE of a SARS-CoV-2 booster or extra primary dose was notably substantial versus primary series vaccination after accounting for variations between SNFs and calendar week. These data suggested that COVID-19 additional primary or booster doses offer significant protection against Omicron variant infections in nursing care residents than the initial series vaccination alone.

From February 14 through March 27, 2022, 15,090 SNFs submitted 89,671 weekly COVID-19 case count reports, while 15,102 SNFs submitted 89,969 weekly resident number reports from January 31 to March 13, 2022. The research incorporated 85,494 records from 14,758 SNFs after matching SNF-level weekly SARS-CoV-2 infections with associated resident data and applying exclusion criteria. The median weekly count of inhabitants documented was 1,126,198, with roughly 22% receiving only the main series vaccination and 65% receiving an extra primary or booster dose. Further, among the care home occupants who were the recipients of a primary series immunization, an extra initial shot, or a booster dose, more than 90% received mRNA-based COVID-19 vaccinations.

Crude weekly confirmed COVID-19 rates decreased in all vaccination cohorts in nursing homes during the research period. Nevertheless, rates of SARS-CoV-2 infection among occupants who received a booster or an additional primary dose were markedly lower than those between unvaccinated residents or inhabitants who received only the primary series vaccine.

About 7,510 confirmed-COVID-19 cases within 1,509,674 residents/weeks were reported in residents with only primary series vaccination, whereas 11,334 confirmed-SARS-CoV-2 cases were reported between 4,416,401 residents/weeks in whom with a booster or additional dose. In addition, the adjusted comparative VE against COVID-19 for booster or extra primary doses compared to just the initial vaccination series vaccine was 46.9%.

Conclusions

The study findings illustrated that a booster or extra SARS-CoV-2 primary vaccine dose imparted higher protection against COVID-19 than only the primary series immunization during the Omicron variant prevalence in nursing home occupants. The authors recommended that all nursing home inhabitants with impaired immunity receive an extra primary COVID-19 vaccine dosage and, if eligible, a booster dose to safeguard against SARS-CoV-2 infection. They also reported that other SARS-CoV-2 preventive techniques, such as vaccination and testing of nursing home visitors and staff members, should be used parallel with the initiatives to keep nursing home occupants abreast on COVID-19 vaccination.

Further, the study suggested that the efficacy and durability of booster or additional main doses against evolving SARS-CoV-2 variants must be assessed by continuously tracking their VE across nursing home inhabitants.