A systematic review found that the efficacy of the COVID-19 vaccine remained high for at least 6 months.

A team of international scientists has recently been published investigating the efficacy of the Coronavirus Disease 2019 (COVID-19) vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and disease severity. We conducted a systematic review of the research. Findings show that the efficacy of the vaccine against severe COVID-19 remains high for 6 months after full vaccination.Surveys are currently available on preprint servers Lancet journal.

study: Vaccine lifetime against SARS-CoV-2 infection and COVID-19 disease: Results of systematic review and meta-regression.. Image Credit: Marco Lazzarini / Shutterstock

Background

As the COVID-19 pandemic progresses, several vaccines have been developed and rigorously tested in clinical trials. Vaccines with satisfactory safety and efficacy status have received emergency use authorization from national public health authorities and the World Health Organization (WHO). Initial assessment of vaccine efficacy within 2-3 months after complete vaccination (immunization by two vaccinations at regular intervals) shows that many vaccines prevent SARS-CoV-2 infection and symptomatic COVID-19. It has been shown to have an efficacy of 85% or more.

However, the recent emergence of breakthrough cases of vaccines in many countries around the world has highlighted the potential for vaccine efficacy to decline over time. Therefore, continuous monitoring of vaccine efficacy is very necessary to inform public health authorities about the need for a third booster.

In the current study, scientists evaluated the duration of vaccine efficacy and disease severity against SARS-CoV-2 infection by systematically reviewing the available literature.

Research design

The analysis included peer-reviewed and preprinted studies published between June and October 2021. The current study analyzed both randomized controlled trials and observational studies investigating the efficacy of the COVID-19 vaccine. Specifically, the analysis included studies comparing fully vaccinated and unvaccinated individuals.

Another series of analyzes was also performed to determine breakthrough infection rates for people vaccinated at different times. Studies that identified cases during SARS-CoV-2 delta development in the population were included only in this analysis.

Important findings

A total of 9,261 studies were initially screened. Of these studies, 14 were finally analyzed to assess the duration of vaccine efficacy. The vaccines evaluated in these studies were BNT162b2 developed by Pfizer / BioNTech, mRNA-1273 developed by Moderna, Ad26.COV2.S developed by Janssen / Johnson & Johnson, and AZD1222 developed by Oxford / Astra Zeneca. was.

Vaccine efficacy against SARS-CoV-2 infection

A total of nine studies confirmed vaccine-specific efficacy data for 6 months after complete vaccination. These studies analyzed the efficacy of the vaccine against SARS-CoV-2 infection. Approximately 89 percent of these studies showed that vaccine efficacy was reduced by more than 10 percent from peak efficacy. In 22 percent of studies investigating the efficacy of Pfizer vaccines against various viral variants, a 25 percent reduction in vaccine efficacy from the peak was observed.

Considering all vaccine efficacy data, regardless of variant type, an 18 percentage point reduction in vaccine efficacy against SARS-CoV-2 infection was observed between 1 and 6 months after vaccination. I did. Considering only the elderly, the decline was almost 20 percentage points.

Vaccine efficacy against symptomatic COVID-19

In one study, including the modelna vaccine, no diminished efficacy for symptomatic COVID-19 was observed for 5 months. Another study using the Pfizer and AstraZeneca vaccines observed a 10 percentage point reduction from the peak for both vaccines.

Considering all vaccine efficacy data, regardless of variant type, a 25 percentage point reduction in vaccine efficacy against symptomatic COVID-19 was observed between 1 and 6 months after vaccination. Considering only the elderly, the decline was 32 percentage points.

Vaccine efficacy against severe COVID-19

Four studies confirmed that there are vaccine efficacy data for severe COVID-19 caused by delta or alpha variants. None of the vaccines evaluated in these studies showed a <70% reduction in efficacy.

Considering all vaccine efficacy data, regardless of variant type, an 8 percentage point reduction in vaccine efficacy against severe COVID-19 was observed between 1 and 6 months after vaccination. rice field. Considering only the elderly, the decrease was 9.7 percentage points.

Vaccine efficacy against delta infection

In studies involving delta breakthrough infections, early recipients of the Pfizer vaccine were observed to have a 1.7-fold higher infection rate than recent recipients. Infectants with the modelna vaccine increased the infection rate by a factor of 1.5.

As for the severity of people over the age of 60, Pfizer vaccine recipients had three times more severe breakthrough infections and 1.6 times more breakthrough infections.

Importance of research

Research reveals it Effectiveness of COVID-19 vaccine for severe illness remained above 70% for at least 6 months after complete vaccination. However, its efficacy against SARS-CoV-2 infection and symptomatic COVID-19 gradually declines over time.

*Important Notices

Preprints are not Lancet publications and are not necessarily reviewed in the Lancet Journal. These preprints are early-stage research papers that have not been peer-reviewed. Findings should not be used in clinical or public health decisions and should not be presented to the general public without emphasizing that they are preliminary and not peer-reviewed.