Young people, healthcare workers and non-white people are among those who are most likely to test positive for Covid-19 after being vaccinated, a new study has found.
Analysis by the Office for National Statistics (ONS) in Britain – where 30 million people have been fully vaccinated and 42 million have received their first jab – found the chance of getting coronavirus after being vaccinated drops sharply 21 days following a first dose.
Just 0.5 per cent of people who had received one dose tested positive for Covid. After two doses this number dropped to 0.07 per cent.
The chart below shows the rate of infection falling after having a vaccine.
For the people who did test positive after vaccination, the study found they were less likely to have a high viral load or develop symptoms.
The ONS study used a 'hazard ratio' to compare the risk of a Covid infection occurring in two different groups at a given time. Someone with a high hazard ratio is more likely to see the hazard happen to them.
These are the factors that influence how likely a person is to test positive after being vaccinated:
The study found age was the biggest factor for a person's chances of getting infected with Covid after vaccination, with the younger people more likely to get infected.
People aged 20 are more than twice as likely to catch Covid than people aged 80 after being vaccinated.
The larger a person's household, the higher their chance of testing positive after vaccination.
The study found people living in a household of one had a hazard ratio of 1, which steadily increased to 1.49 for people living in households of five or more people.
The study found non-white people were more likely to catch Covid than white people.
White people had a hazard ratio of 1 while non-white people had a hazard ratio of 1.18.
The ONS found gender did not play much of a role in the likelihood of catching Covid after getting vaccinated with only a 0.03 difference between males and females.
Men were slightly higher at a hazard ratio of 1 compared to women's hazard ratio of 0.97.
A significant factor in increasing the chance of catching COVID after getting vaccinated was if the person was a patient-facing healthcare worker.
As might be expected, someone who worked with patients' hazard ratio was higher (1.31) than those who did not (1).
Prof Kevin McConway, Emeritus Professor of Applied Statistics at The Open University, said: “In the analysis of characteristics of people who tested positive after vaccination, the groups who were more likely to be infected after vaccination mostly correspond to the groups who would be more likely to be infected even if they weren’t vaccinated – people working in patient-facing health care and in care homes, those living in larger households, in areas of higher deprivation, and in rural villages rather than large urban areas.
"None of that is very surprising, I think.
"Generally, there’s quite a strong effect of age, with younger people showing a considerably higher risk of infection after vaccination than older people."
Connor Parker, Yahoo News UK
Do you have a story tip? Email: firstname.lastname@example.org