The decision by US President Donald Trump's administration to terminate 22 federal contracts for mRNA-based vaccines is a major blow to a hugely promising platform, the World Health Organization said on Thursday.
The announcement made by Health Secretary Robert F. Kennedy Jr. marked his latest effort to weave vaccine skepticism into the core of US government policy.
"This is, of course, a significant blow," WHO immunisation figurehead Joachim Hombach told the UN correspondents' association ACANU.
"mRNA vaccines are a very important technology and platform which has served us extremely well for Covid. We also know there is very promising work going on in relation to influenza vaccines.
"From our perspective, the platform is particularly useful in relation to developing vaccines against emerging and pandemic threats, because these platforms can be very rapidly adapted."
Unlike traditional vaccines, which often use weakened or inactivated forms of the target virus or bacteria, mRNA shots deliver genetic instructions into the host's cells, prompting them to produce a harmless decoy of the pathogen and train the immune system to fight the real thing.
The US health department's Biomedical Advanced Research and Development Authority is "terminating 22 mRNA vaccine development investments because the data show these vaccines fail to protect effectively against upper respiratory infections like COVID and flu", Kennedy said.
Hombach -- executive secretary for the WHO's strategic advisory group of experts on immunisation -- called for work on the development of mRNA vaccines to continue around the world.
"This is, from our perspective, an unfortunate and untimely move but we are confident that the research endeavour will continue because it's an extremely promising technology," he told reporters.
Shortly after his inauguration in January, Trump signed an executive order directing the United States to withdraw from the WHO, an organisation he has repeatedly criticised over its handling of the Covid-19 pandemic.
