<p>The World Health Organization's chief scientist on Monday advised against people mixing and matching Covid-19 vaccines from different manufacturers, calling it a "dangerous trend" since more data is needed about the health impact.</p>.<p>"It's a little bit of a dangerous trend here," Soumya Swaminathan told an online briefing. "It will be a chaotic situation in countries if citizens start deciding when and who will be taking a second, a third and a fourth dose."</p>.<p><strong>Read more: <a href="https://www.deccanherald.com/international/who-says-countries-should-not-order-covid-19-boosters-while-others-still-need-vaccines-1007955.html" target="_blank">WHO says countries should not order Covid-19 boosters while others still need vaccines </a></strong></p>.<p>Swaminathan called mixing a "data-free zone" on Monday but the WHO clarified on Tuesday that some data was available and more was expected.</p>.<p>Its Strategic Advisory Group of Experts on vaccines in June said the Pfizer vaccine could be used as a second dose after an initial dose of AstraZeneca, if the latter is not available.</p>.<p>The results of a further clinical trial led by the University of Oxford that will look at mixing AstraZeneca and Pfizer as well as Moderna and Novovax vaccines is underway.</p>.<p>"Data from mix and match studies of different vaccines are awaited - immunogenicity and safety both need to be evaluated," the WHO said in emailed comments.</p>.<p>It should be public health agencies who make decisions, based on available data, and not individuals, the WHO added.</p>
<p>The World Health Organization's chief scientist on Monday advised against people mixing and matching Covid-19 vaccines from different manufacturers, calling it a "dangerous trend" since more data is needed about the health impact.</p>.<p>"It's a little bit of a dangerous trend here," Soumya Swaminathan told an online briefing. "It will be a chaotic situation in countries if citizens start deciding when and who will be taking a second, a third and a fourth dose."</p>.<p><strong>Read more: <a href="https://www.deccanherald.com/international/who-says-countries-should-not-order-covid-19-boosters-while-others-still-need-vaccines-1007955.html" target="_blank">WHO says countries should not order Covid-19 boosters while others still need vaccines </a></strong></p>.<p>Swaminathan called mixing a "data-free zone" on Monday but the WHO clarified on Tuesday that some data was available and more was expected.</p>.<p>Its Strategic Advisory Group of Experts on vaccines in June said the Pfizer vaccine could be used as a second dose after an initial dose of AstraZeneca, if the latter is not available.</p>.<p>The results of a further clinical trial led by the University of Oxford that will look at mixing AstraZeneca and Pfizer as well as Moderna and Novovax vaccines is underway.</p>.<p>"Data from mix and match studies of different vaccines are awaited - immunogenicity and safety both need to be evaluated," the WHO said in emailed comments.</p>.<p>It should be public health agencies who make decisions, based on available data, and not individuals, the WHO added.</p>