Coronavirus: Vaccine immunity starts waning after six months, study finds

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Health experts are calling for the rollout of COVID-19 vaccine booster doses after a study found that immunity starts waning six months after the second dose.


The Pfizer (NYSE:PFE) Inc jab saw protection reducing to 74%, from 88% a month after the second dose, while AstraZeneca PLC (LSE:AZN) saw the figure going down to 67% from 77%, according to the ZOE COVID Study.


READ: US issues full approval for Pfizer vaccine


Researchers stressed the importance of having as many people as possible being fully vaccinated, which helps those who can’t get the jab such as children and people with weakened immune systems who don’t respond as well to it.


“A reasonable worst-case scenario could see protection below 50% 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,” said Professor Tim Spector, lead scientist at the ZOE COVID Study.


“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.”


ZOE is one of the largest real-life vaccine effectiveness studies on record, as over 1mln people upload test results and symptoms on a daily basis.


The six-month safety and effectiveness trial of the Pfizer (NYSE:PFE) 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.


The findings had a slightly lower level of protection to start with compared to what Pfizer and AstraZeneca had found in their trials.


“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,” scientists at ZOE said.


“This 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.”

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