Two vaccines made using messenger RNA (mRNA) have proved spectacularly successful at warding off COVID-19, but a third mRNA-based candidate has flopped in a final-stage trial, according to an initial report released this week. Researchers are now asking why — and some think that choices about the type of mRNA chemistry used might be to blame. Any insight could help to guide the future design of mRNA vaccines against COVID-19 or other diseases.
The company behind the beleaguered trial, CureVac, based in Tübingen, Germany, announced preliminary data on 16 June from a 40,000-person trial, which showed that its two-dose vaccine was just 47% effective at preventing disease.
CureVac’s mRNA vaccine was expected to be cheaper and to last longer in refrigerated storage than the earlier mRNA vaccines made by Pfizer–BioNTech and Moderna. Many had hoped that it could help to expand the reach of mRNA-based vaccines in lower-income countries, and European countries were expecting to order hundreds of millions of doses.
Antibiotic Prescriptions Associated With COVID-19 Outpatient Visits Among Medicare Beneficiaries, April 2020 to April 2021
Outpatient Visits for COVID-19 and Associated Antibiotic Prescriptions Among Medicare Beneficiaries Aged 65 Years or Older, by Setting, US, April 2020 to April 2021. The volume of COVID-19 visits differed by setting: emergency department, 525 608 (45.8% of all visits); office, 295 983 (25.3%); telehealth, 260 261 (22.3%); and urgent care, 77 268 (6.6%).
Source: Journal of American Medical Association Network