After COVID-19, fully-vaccinated patients may be as likely to infect loved ones as unvaccinated patients.
Fully vaccinated COVID patients are just as contagious to others in their households as infected unvaccinated people, says new study.
Your home is a crucial environment for Covid infection transmission, with frequent daily contact with an infected person associated with an increased risk of contracting the virus.
However, there are still unanswered questions, such as the true proportion of household contacts who become infected after an initial case, the duration of their infection, and the effect of vaccination on the danger of transmitting the virus and the likelihood of contracting it.
A new study has found that, while Covid vaccination is critical for preventing severe disease and death, even those who have been fully vaccinated can contract the virus and pass it on to others.
Researchers from Imperial College London and the UK Health Security Agency (HSA) disclose their findings in the Lancet, detailing how they analyzed data from 204 household connections of 138 persons infected with the Delta variant.
53 of these contacts became infected after being recruited within five days of their household member showing symptoms and tested daily for 14 days; 31 were fully vaccinated and 15 were unvaccinated.
The findings suggest that even those who are fully vaccinated face a significant risk of infection, with analysis revealing that a fully vaccinated contact has a 25% chance of contracting the virus from an infected household member, while an unvaccinated contact has a 38% chance of contracting the virus.
The data, however, do not reveal the degree of disease, and the team warns that the figures are within a range of potential values, so the precise extent of the difference is unknown.
According to the findings, whether an infected person is completely vaccinated or not makes little or no difference in terms of how infectious they are to their household connections.
The researchers go on to say that the peak level of virus in affected patients was the same whether they were vaccinated or not, but these levels dropped off faster in the vaccinated participants, implying that they cleared the infection faster.
“This likely explains,” said prof Ajit Lalvani – one of the authors of the study, “why, [fully vaccinated] breakthrough cases are as infectious to their contacts as [unvaccinated] cases.”
The team also took a closer look at people who had received all of their vaccinations.
“What we found, surprisingly, was that already by three months after receipt of the second vaccine dose, the risk of acquiring infection was higher compared to being more recently vaccinated,” said Lalvani.
“This suggests that vaccine-induced protection is already waning by about three months post-secondary,” he added.
Lalvani underlined the need of vaccination, including boosters, stressing that unprotected people cannot rely on those who have been completely vaccinated for protection.
Should a fully vaccinated person become infected, he added, they will be protected from serious disease and death, and will likely only have a mild infection.
When questioned if the statistics indicated that booster doses should be given sooner than six months following a second jab, Lalvani said the focus should be on encouraging people who are already eligible to take the additional dosage.
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