Vaccinated Individuals Can Transmit COVID-19 At Home: Lancet Study

London: Fully vaccinated people can contract and pass on Delta variant of SARS-CoV-2, the virus that causes COVID-19, in household settings, but at lower rates than unvaccinated people, according to a study published in The Lancet Infectious Diseases journal. Researchers led by Imperial College London, UK, found that vaccinated people clear the infection more quickly, but the peak viral load among them is similar to that seen in unvaccinated individuals, which may explain why they can still readily pass on the virus at home. The researchers noted that most COVID-19 transmission is known to occur in households yet there is limited data on the risk of transmission of the Delta variant from vaccinated people with asymptomatic or mild infections in the community.

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Vaccines are critical to controlling the pandemic, as we know they are very effective at preventing serious illness and death from COVID-19, said Professor Ajit Lalvani of Imperial College London, who co-led the study. However, our findings show that vaccination alone is not enough to prevent people from being infected with the Delta variant and spreading it in household settings, Mr Lalvani added.

The researchers noted that the transmission between vaccinated people makes it essential for unvaccinated people to get immunised to protect themselves from acquiring infection and severe COVID-19, especially as more people will be spending time inside in close proximity during the winter months. The study enrolled 621 participants, identified by the UK contact tracing system, between September 2020 and September 2021. All participants had mild COVID-19 illness or were asymptomatic. They had daily PCR tests to detect infection, regardless of whether or not they had symptoms. The researchers performed PCR tests on swab samples provided daily by each participant for 14-20 days.

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Changes over time in viral load — the amount of virus in a person’s nose and throat — were estimated by modelling PCR data. A total of 205 household contacts of Delta variant index cases were identified, of whom 53 tested positive for COVID-19. Among vaccinated contacts infected with the Delta variant, the median length of time since vaccination was 101 days, compared with 64 days for uninfected contacts, the researchers said.

This suggests that the risk of infection increased within three months of receiving a second vaccine dose, likely due to waning protective immunity, they said. The authors point to vaccine waning as important evidence for all eligible people to receive booster shots. A total of 133 participants had their daily viral load trajectories analysed, of whom 49 had pre-Alpha variant and were unvaccinated, 39 had Alpha and were unvaccinated, 29 had Delta and were fully vaccinated, and 16 had Delta and were unvaccinated.

The study found that the viral load declined more rapidly among vaccinated people infected with the Delta variant compared with unvaccinated people with Delta, Alpha, or pre-Alpha. However, the authors note that vaccinated people did not record a lower peak viral load than unvaccinated people, which may explain why the Delta variant can still spread despite vaccination as people are most infectious during the peak viral load phase.

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Understanding the extent to which vaccinated people can pass on the Delta variant to others is a public health priority, said Anika Singanayagam, co-lead author of the study. By carrying out repeated and frequent sampling from contacts of COVID-19 cases, we found that vaccinated people can contract and pass on infection within households, including to vaccinated household members, Ms Singanayagam said.

The findings suggest that continued public health and social measures to curb transmissions – such as mask wearing, social distancing, and testing – remain important, even in vaccinated individuals. The authors acknowledge some limitations to their study. Due to the nature of UK symptoms-based community testing, only contacts of symptomatic index cases were recruited, the researchers said. As the study was undertaken when infection was circulating widely, it cannot be excluded that another household member may already have been infected and transmitted COVID-19 to the index case, they added.

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NDTV – Dettol have been working towards a clean and healthy India since 2014 via Banega Swachh India initiative, which is helmed by Campaign Ambassador Amitabh Bachchan. The campaign aims to highlight the inter-dependency of humans and the environment, and of humans on one another with the focus on One Health, One Planet, One Future – Leaving No One Behind. It stresses on the need to take care of, and consider, everyone’s health in India – especially vulnerable communities – the LGBTQ population, indigenous people, India’s different tribes, ethnic and linguistic minorities, people with disabilities, migrants, geographically remote populations, gender and sexual minorities. In wake of the current COVID-19 pandemic, the need for WASH (Water, Sanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign will continue to raise awareness on the same along with focussing on the importance of nutrition and healthcare for women and children, fight malnutrition, mental wellbeing, self care, science and health, adolescent health & gender awareness. Along with the health of people, the campaign has realised the need to also take care of the health of the eco-system. Our environment is fragile due to human activity,  that is not only over-exploiting available resources, but also generating immense pollution as a result of using and extracting those resources. The imbalance has also led to immense biodiversity loss that has caused one of the biggest threats to human survival – climate change. It has now been described as a “code red for humanity.” The campaign will continue to cover issues like air pollution, waste management, plastic ban, manual scavenging and sanitation workers and menstrual hygiene. Banega Swasth India will also be taking forward the dream of Swasth Bharat, the campaign feels that only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and the country can become a Swasth or healthy India.