Moderna vaccine effectiveness turns negative within months

The effectiveness of Moderna’s COVID-19 vaccine against infection turns negative over time, according to a new study that was funded by the vaccine maker.

The effectiveness of three doses—a primary series and a booster—against infection remained above 50 percent after 150 days against BA.1, a subvariant of the Omicron virus variant, researchers estimated.

However, against more recent strains, including the currently dominant BA.5, the effectiveness turned negative. Against BA.2, BA.4, and BA.5, the effectiveness went negative after 150 days; against BA.1.12.1, the effectiveness turned negative after 91 days.

Negative effectiveness means that a vaccinated person is more likely to contract COVID-19, the disease caused by the virus, than an unvaccinated person.