There are growing fears that the effectiveness of the World’s COVID vaccines will fade in the space of six months, leaving the most vulnerable poorly protected.
It has prompted a call for an immediate launch of a booster programme to enhance the vaccine effectiveness for those most at risk of death of serious illness from the disease.
With nearly 42 million people receiving both doses in less than eight months in the UK since December some research studies are now suggesting that the protection provided by the vaccines may start to wear off over time, especially against the now-dominant Delta variant.
An analysis of data from the ZOE COVID Study showed that the protection provided by two doses of either the Pfizer or AstraZeneca vaccine wanes over a number of months.
The team analysed data recorded by ZOE COVID Study app contributors who logged their COVID vaccinations between December 8, 2020, and July 31, 2021. They then looked to see whether any of these people reported a positive COVID test result between May 26 this year, when the Delta variant became dominant in the UK, and the end of July.
This analysis included:
- 411,642 test results from users who were doubly vaccinated with the Pfizer mRNA vaccine at the time of the infection
- 709,486 test results from users who were doubly vaccinated with the AstraZeneca vaccine
- 76,051 test results from users who were not yet vaccinated at the time of the infection
“We found that initial protection against infection a month after the second dose of the Pfizer vaccine was 88%, while after five to six months this fell to 74%,” said the study authors. “For the AstraZeneca vaccine, there was around 77% protection a month after the second dose, falling to 67% after four to five months.”
With more than 1.2 million test results and participants, this is one of the largest real-life vaccine effectiveness studies on record.
The six month safety and effectiveness trial of the Pfizer vaccine, which were carried out when the original Alpha variant was dominant, showed that the jab provided a 96.2% reduction in infection risk up to 2 months after the second dose, with an 83.7% reduction after more than 4 months.
“Our findings show that in the real world there is a slightly lower level of protection to start with, as well as a more pronounced wane over time,” added the authors. “This could be for many reasons, including a greater number of people with underlying health conditions in the general population compared to trial participants and variability in how the vaccines were stored and administered.”
The authors added it means that the majority of people who had their second dose five to six months ago will be older or vulnerable due to other health reasons, placing them at increased risk of COVID-19 compared to those vaccinated more recently.
“Vaccines still provide high levels of protection for the majority of the population, especially against the Delta variant, so we still need as many people as possible to get fully vaccinated,” said the study. “Importantly, not only does your vaccine help to protect you, it also protects those around you who aren’t yet vaccinated. This includes children and people with weakened immune systems who don’t respond as well to the vaccine.”
The discovery that vaccine-induced immunity against COVID-19 fades over time is not unexpected, although it might require a new vaccination strategy over the coming months.
Professor Tim Spector, lead scientist at the ZOE COVID Study, explained: “A reasonable worst-case scenario could see protection below 50 percent for the elderly and healthcare workers by winter. With high levels of infection in the UK, driven by loosened social restrictions and a highly transmissible variant, this scenario could mean increased hospitalisations and deaths.
“We urgently need to make plans for vaccine boosters, and based on vaccine resources, decide if a strategy to vaccinate children is sensible if our aim is to reduce deaths and hospital admissions.”