According to a study by Professor Neil Fergusson, nicknamed “Professor Lockdown,” people who have been double-vaccinated with the coronavirus vaccine still have a one in four chance of contracting COVID from an infected family member.
According to researchers at Imperial College London, this happens even if the infected person was fully vaccinated himself in the so-called case of a vaccine breakthrough.
But, according to the Daily Mail, the risk for unvaccinated family members was even higher: the likelihood of contracting the virus from infected family members was 38 percent.
Scientists were “surprised” to find that the protection afforded by the COVID vaccines began to diminish significantly just three months after the second dose. They say the results make it more important for people than ever to get booster shots.
The study, commissioned by the UK government, covered the jabs of Pfizer and AstraZeneca and reached over 600 Britons. Scientists have also found that vaccination does not matter how likely someone is to contract COVID, and this may be why the Delta variant is still so common.
But vaccinated people recover faster from the virus, resulting in less severe and shorter symptoms, and vaccination lowers a person’s chances of contracting COVID in the first place.
The researchers said this study is important given that the home is where COVID is most commonly transmitted between people due to the frequency of contact in smaller, less ventilated areas.
One study author said it showed that the unvaccinated cannot rely on a shot for protection.
Professor Ajit Lalwani, head of the Department of Infectious Diseases at Imperial College London, who participated in the study, says the results show there is still a significant chance of infection, even if you get the COVID-19 vaccine. “Even if this person is double-vaccinated, they can pass the infection on to other family members,” he said. “About one in four people who become infected in a family contract an infectious disease, which is quite a large number.”
But Professor Lalwani said the risk of contracting the coronavirus is even higher for unvaccinated family members, which proves the benefits of vaccination. “When we looked at unvaccinated people who came into contact with them at home, their risk of infection was about 38 percent,” he said. “This means the vaccine is still effective in reducing the risk of transmission, in this case from 38 to 25 percent.”
However, Professor Lalwani explained that the real difference was what happens after infection. “Most importantly, because they are vaccinated twice, they usually only get mild illness or asymptomatic infection,” he said. “When they (unvaccinated) are infected, they are at risk of serious illness, hospitalization and death.”
Professor Lalwani said the study also showed that it took only three months for a fully pricked person to experience a decrease in COVID protection. “Surprisingly, just three months after receiving the second dose of the vaccine, the risk of infection was higher than with the recent vaccination,” he said.
While the scientists said their sample size of about 600 households was too small to measure this weakened immunity, they said it shows the importance of getting a COVID booster when eligible.
Another aspect of the study was to examine the difference in viral load between vaccinated and unvaccinated people who contracted COVID. Viral load indicates how much virus is in a substance, in the case of COVID, this means how much virus is present in the upper respiratory tract, mouth, nose and throat.
Prof Lalwani explained that the researchers found that vaccination status does not affect the amount or timing of peak infectivity when people are most likely to transmit the virus to others. “The vaccination did not affect the time people spent during the period of maximum infectiousness,” he said.
This infectivity window usually appears three to four days after infection and before symptoms of COVID appear. The fact that the Covid vaccine does not affect this critical period of coronavirus transmission may explain why the Delta variant remains so contagious despite widespread vaccination.
Prof Lalwani said vaccinations have indeed made a difference after the peak when the body starts producing antibodies to fight the virus.
“The effect of vaccination is to accelerate the decline in the viral pathway in the upper repositories so that people get rid of the viral infection faster, which is good news,” he said. “This helps explain why vaccinated people, even if they are infected, have fewer symptoms, clear them up more quickly and, crucially, have a much lower risk of developing serious illness.”
The scientist added that this also means that the unvaccinated cannot rely on the injection for protection. “Therefore, unvaccinated people cannot rely on the immunity of the vaccinated population for protection,” he said. “They are still at risk of infection and the risk of serious illness and death.”
Prof Lalwani said the conclusion from the study was that vaccinations and revaccinations are necessary, especially given the winter months when people spend more time together indoors, with only a few weeks left. “Therefore, the greatest possible vaccination coverage and timely booster doses are needed to combat COVID,” he said. “If people have not yet been vaccinated, they should be vaccinated, and people who have received the vaccines and who are eligible for the booster should receive that booster as soon as possible.”
Dr Anika Shinganayagam, co-lead author of the study, said the study has shown the importance of maintaining some COVID restrictions, even for those vaccinated. “Thus, sustained public health and social measures to limit transmission – such as wearing disguises, social distancing and testing – remain important even for vaccinated individuals,” she said.
The study, published in The Lancet Infectious Diseases, involved 621 participants contacted by NHS Track and Trace between September 2020 and September 2021. Of these, 163 were infected with Covid and had 233 contacts. Participants were tested daily using PCR tests for 20 days to measure their viral load, and their vaccination status was recorded.
Professor Ferguson, who also participated in the study, said the effectiveness of the COVID booster program, whose slow pace has been criticized, will be key to keeping the pandemic under control.
A key government adviser, whose modeling triggered the first lockdown last March, said it was too early to tell if UK COVID cases were at their peak, but added that there were encouraging signs. “We’ll have to wait at least a couple of weeks, if not closer to three, to be sure, but there are some encouraging signs in terms of declining cases.”
Professor Ferguson said the success of the revaccination program will be key to keeping COVID under control this winter, although he added that predictions remain uncertain.
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