A study of Covid-19 antibody levels using home test kits found that people who have had two vaccine doses had a 4,500% average increase in antibody levels compared to those who had only one.
The trial, which was conducted by home testing company YorkTest, included people who were fully vaccinated, those who had only received a single dose and people who had been previously diagnosed with Covid-19 and were unvaccinated. The vaccinated participants had not knowingly contracted Covid-19 in the past.
The study of 46 participants used YorkTest’s Covid-19 Immunity Tracker Test, which is designed to give users an idea of their Covid-19 antibody status.
The British Medical Journal has defined a high level of Covid-19 antibody protection as being over 250 U/ml.
The YorkTest trial found that after one dose of a vaccine average antibody levels were 24 U/ml, climbing to 1,084 U/ml after both doses.
Participants who had recovered from Covid-19 but who had not been vaccinated had higher average levels of antibodies than those who have only received a single vaccine. After recovering from Covid-19 without being vaccinated, average antibody levels were 95 U/ml.
The average level of antibodies to Covid-19 was 997 U/ml up to 100 days after the second dose of a vaccine, which then increased by 25% to an average of 1,242 U/ml between 100 and 171 days.
Combined with emerging data indicating an eventual reduction in antibodies, this suggests peak protection three to six months after receiving a second vaccine.
YorkTest scientific director Dr Gill Hart said these results suggest that more people should be able to access antibody tests.
Hart said: “Although results of our initial trials show that immunity is reaching its highest point three to six months after a second vaccine dose, there is some suggestion that antibody levels may start to decrease from that point.
“Our study is ongoing and the government has already announced plans to provide antibody tests to those testing positive following a PCR test. However, our results show there’s an argument for antibody testing to be rolled out more widely.
“People need to be mindful of their own antibody levels so they can make informed decisions about their day-to-day lives. Granted, we have heard that a booster programme is coming but we still don’t know when that will be and who will be included.
“Our trial continues and we have now entered the crucial phase where we start monitoring antibody levels six-nine months after a second vaccine dose.”