Nursing Home Study Shows Fourth COVID mRNA Dose Offers Extra Protection Against Severe Omicron Outcomes

In a recent study posted on medrex sib* In a preprint server, Canadian researchers evaluated the efficacy of protection induced by a fourth dose of the coronavirus disease 2019 (COVID-19) mRNA vaccine.

Long-term care (LTC) residents who received a third dose of COVID-19 vaccine at least three months prior were eligible to receive a fourth dose from December 30, 2021 in Ontario, Canada. The most popular fourth dose supplement was 100 micrograms (mcg) of messenger ribonucleic acid (mRNA)-1273. A previous study comparing vaccine efficacy (VE) in unvaccinated and marginalized individuals showed that a fourth dose received 7 days earlier was associated with severe acute respiratory syndrome coronavirus 2 (SARS -CoV-2) enhanced protection against Omicron infection, symptomatic infection and severe outcome. Efficacy associated with the 4th and her 3rd vaccinations.

study: Efficacy and duration of protection from the fourth dose of COVID-19 mRNA vaccine in long-term care residents of Ontario, CanadaImage Credit: Oxanaso/Shutterstock

About research

In the current study, researchers determined the marginal vaccine efficacy of a fourth dose of COVID-19 vaccination compared to a third dose in LTC residents.

The team will use laboratory data, vaccines, reportable diseases, and health care data from December 30, 2021 to August 3, 2022 to identify LTC residents aged 60 and over as of December 30, 2021. A negative test study was conducted. The SARS-CoV -2 Omicron variant was the main variant of concern (VOC) across the analyses. Therefore, until delta (B.1.617.2) was determined by either whole-genome sequencing or spike (S) gene target impairment, patients were assumed to be infected with omicron.

The team assessed VE corresponding to 2-, 3-, and 4-dose vaccinated individuals and unvaccinated individuals. In addition, results regarding marginal efficacy associated with his 4 doses versus his 3 doses administered 3 months earlier and hospitalizations or mortality rates wholly or partially due to COVID-19 severity was estimated. Case and control samples were collected up to the week prior to testing. Primary infections were selected when there were a large number of infections. For controls, the first negative test within the previous week was selected. If controls are negative in the early weeks but positive later in the study period, they may be considered cases later.

The team used logistic regression to estimate the odds of vaccination for cases while adjusting for age, sex, region of residence, week of testing, and SARS-CoV-2 testing >90 days prior to testing negative control cases. compared to A framework of generalized estimating equations with exchangeable correlation structures was adopted to account for clustering at the facility level. VE and marginal effects were calculated using the adjusted odds ratios in Equation 1.

result

Nearly 92% of Ontario LTC residents were tested for SARS-CoV-2 at least once during the study period. At the time of testing, 46.3% of cases and 48.7% of controls had received her fourth vaccination. The patient who received her 4th dose resided in a hospital with an active outbreak, compared with the patient who received her 3rd dose 84 days earlier. In addition, 57% and 95% of individuals who received at least 3 or 4 vaccinations received mRNA-1273.

Compared to patients who received the third dose, the fourth dose administered 84 days earlier had marginal efficacy against infections of 23%, symptomatic infections of 36%, and severe outcomes of 37%. Protection against infections and symptomatic infections was from approximately 112 to 139 days, and minimal protection against severe outcomes up to 168 days, with efficacy declining over time after the fourth dose. VE increased among vaccinated individuals after each subsequent dose, but decreased over time after vaccination.

VE peaked less than 84 days after the fourth dose, with 49% VE for infections, 69% symptomatic infections, and 82% severe outcomes. VE decreased to 18% for infection, 44% for symptomatic infection, and 74% for severe outcome approximately 168 days after the fourth vaccination.

Overall, the findings showed that: efficacy of The fourth dose of mRNA COVID-19 vaccine on outcomes for SARS-CoV-2 Omicron infection in LTC patients in Ontario decreased over time and peaked shortly after receiving the fourth dose.

*Important Notices

medrex sib We publish a non-peer-reviewed, preliminary scientific report and should not be taken as conclusive, to guide clinical practice/health-related actions, or to be treated as established information.