COVID-19 vaccination reduces mortality risk, but only for 6 months

New research from the UK Health Security Agency (UKHSA) has presented significant findings regarding the efficacy of COVID-19 vaccination. 

The experts found that there is a substantial decrease in the risk of death from COVID-19 following vaccination. However, they also found evidence that this protective effect diminishes after six months.

Focus of the study

“Risk of death after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has fallen during the pandemic, largely due to immunity from vaccination. In England, the timing and extent of this reduction varied due to staggered eligibility during the primary vaccination campaign, based on age and clinical risk group,” wrote the study authors. 

“Duration of protection is less well understood. Our objective was to estimate the case fatality risk (CFR) by vaccination status and time since last dose during a period of widespread community testing, to better understand the impact of coronavirus disease 2019 (COVID-19) vaccination and duration of protection.”

Case fatality risk 

The researchers analyzed over 10 million COVID-19 cases in adults from May 2020 to February 2022. The team focused on case fatality risk (CFR), which is the proportion of COVID-19 cases that result in death. 

This metric was cross-referenced with the vaccination status of individuals, uncovering a strong correlation between vaccination and lowered mortality rates.

“Case fatality risk (CFR) has been a useful metric for observing changes in mortality during the pandemic. When testing patterns are stable, this measure can show changes in risk of death over time, highlighting groups at higher risk of severe disease or death,” wrote the researchers.

Key findings

A critical observation from the study is the time-sensitive nature of vaccine efficacy. The data indicates that within six months of receiving the last vaccine dose, CFR was consistently lowest across all age groups. 

Beyond this six-month period, the experts observed an increase in case fatality risk, suggesting a waning protective benefit from the vaccine.

Impact on mortality rates

The study highlights the success of the COVID-19 vaccination program in reducing mortality rates, particularly among adults over 50. In this group, there was a sharp contrast in CFR between vaccinated and unvaccinated individuals. 

The CFR was 10 times higher in unvaccinated adults (6.3%) compared to those vaccinated within six months of testing positive for COVID-19 (0.6%). Furthermore, the study revealed a significant decline in CFR in early 2021, coinciding with the initial vaccine rollout.

Study significance 

Study lead author Florence Halford from the UKHSA’s COVID-19 Vaccines and Epidemiology Division emphasized the importance of these findings.

“COVID-19 Case Fatality Risk reduced after vaccination, with the lowest seen across all age bands when vaccinated up to six months prior to the specimen date. This provides some evidence for continued booster doses in older age groups,” said Halford.

Booster doses

The research offers strong evidence supporting the need for booster doses, especially in older populations. 

As the protective effects of the vaccine diminish over time, regular booster doses could be crucial in maintaining low mortality rates amidst the ongoing pandemic.

The study is published in the Journal of the Royal Society of Medicine.

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