The company expressed surprise and confusion about the decision, noting the FDA’s earlier support for the study plan.
The perceived safety of the MMR vaccine is now 83% (down from 86%).
The findings of the meta-analysis draw on data from more than 23 million people.
The vaccine is 40% against medically attended infection with influenza A(H3N2) viruses, 37% against subclade K of the H3N2 strain, and 31% against H1N1 influenza A.
Of adults ages 50 and older, 42% remain unvaccinated.
The market size for seasonal influenza vaccines is large and will remain so for the foreseeable future.
The company, however, continues to work on a phase 1/2 study of its H5 mRNA flu vaccine for pandemic preparedness.
Vaccine effectiveness against severe illness was 43% among children with underlying conditions and 53% among those without.
Older adults have higher risks of certain diseases because they have more underlying illnesses and because immune systems weaken with age.
Despite a partial vaccine mismatch this season, say researchers, vaccine effectiveness was statistically significant across all age-groups.
