Scientists speculate that one of the most important means of putting an end to the ongoing pandemic is rapid vaccination.
Numerous studies looked into the effectiveness of the available COVID-19 vaccines in the general population.
Some studies suggested that the Pfizer-BioNTech and the Oxford-AstraZeneca vaccines were highly efficient against the Alpha and preceding variants.
Due to mutations, a rise in the number of SARS-CoV-2 variants was observed, which is a direct threat to the effectiveness of the vaccines.
The Delta variant led to a striking increase in the number of reported cases in numerous countries across the globe, including those with increased vaccination rates, like the UK.
The Delta variant was labeled as a Variant of Concern in numerous countries due to its ravaging impact on the population.
A recent study published on the medRxiv preprint server looked into the effectiveness of the BNT162b2, ChAdOx1, and mRNA-1273 vaccines by using SARS-CoV-2 PCR-positive tests.
The study relied on a community-based survey of individuals living in certain private households across the United Kingdom.
The RT-PCR tests were conducted in the households on a pre-set schedule.
The study was carried out in two phases: The first phase was between 1 December 2020, at the beginning of the vaccination program, and 16 May 2021. In that time interval, the Alpha variant was dominant.
The second phase was delimited between 17 May 2021 and 1 August 2021, when the Delta variant became prevalent.
Researchers also looked into the variation in vaccine effectiveness according to long-term health conditions among individuals split into two age groups: 18-34 years and 35-65 years.
The viral burden was determined via Ct values among newly infected patients who became PCR-positive after two weeks of receiving the final dose of a vaccine.
In conclusion, the study says that the BNT162b2 and ChAd0x1 vaccines registered a decrease in effectiveness against the Delta variant compared to other variants, like the Alpha strain.
Also, the study discovered that a single dose of the mRNA-1273 vaccine had comparable (or better) effectiveness than a single dose of the BNT162b2 or ChAdOx1.
The immune response of the two-dose vaccine was compared to the immune protection that naturally occurs after contracting the virus.