Mix-and-match Vaccines Highly Effective Against COVID-19: Lancet Study

London: People who received a first dose of the Oxford-AstraZeneca COVID-19 vaccine followed by an mRNA vaccine shot had a lower risk of infection compared to those immunised with both doses of the AstraZeneca preventive, according to a nationwide study in Sweden. Since the use of AstraZeneca’s vector-based vaccine against COVID-19 was halted for people younger than 65 years of age due to safety concerns, all individuals in Sweden who had already received their first dose of this vaccine were recommended an mRNA vaccine as their second dose.

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Having received any of the approved vaccines is better compared to no vaccine, and two doses are better than one, said Peter Nordstrom, a professor at Umea University, Sweden.

“However, our study shows a greater risk reduction for people who received an mRNA vaccine after having received a first dose of a vector-based, as compared to people having received the vector-based vaccine for both doses,” Mr Nordstrom said.

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The study, published in The Lancet Regional Health – Europe journal on Monday (October 18), is based on nationwide registry data from the Public Health Agency of Sweden, the National Board of Health and Welfare, and Statistics Sweden. In the main analysis, about 700,000 individuals were included.

During a 2.5-month average follow-up period after the second dose, the study showed a 67 per cent lower risk of infection for the combination of AstraZeneca and Pfizer vaccine shots. There was a 79 per cent lower risk of infection for AstraZeneca and Moderna vaccine shots, compared to unvaccinated individuals, the researchers said. For people having received two doses of the AstraZeneca vaccine, known as Covishield in India, the risk reduction was 50, they said. These risk estimates were observed after accounting for differences regarding date of vaccination, age of the participants, socioeconomic status, and other risk factors for COVID-19.

The researchers noted that the study estimates of effectiveness apply to infection with the Delta variant, which was dominating the confirmed cases during the follow-up period

The results of the study may have implications for vaccination strategies in different countries, said Marcel Ballin, doctoral student at Umea University, and co-author of the study.

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“The World Health Organization has stated that despite the promising results from previous studies regarding immune response from mix-and-match vaccination, there is a need for larger studies to investigate their safety and effectiveness against clinical outcomes. Here we now have one such study,” Marcel Ballin said.

There was a very low incidence of adverse thromboembolic events, or formation of blood clots in blood vessels, for all vaccine schedules, according to the researchers. The number of COVID-19 cases severe enough to result in inpatient hospitalisation was too low for the researchers to be able to calculate the effectiveness against this outcome. Past studies have demonstrated that mix-and-match vaccine schedules generate a robust immune response. However, it has been unclear to which extent these schedules may reduce the risk of clinical infection, the researchers said, adding that their study aimed to fill that knowledge gap.

Also Read: COVID-19 Vaccines Effective Against Delta Variant Of Novel Coronavirus: US Study

(This story has not been edited by NDTV staff and is published from a syndicated feed.)

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.