Studies show that a fourth mRNA vaccine dose offers the elderly and other high-risk groups strong protection against hospitalization and death from COVID-19, but experts say benefits for other populations may be more limited.
Both Pfizer and GSK have shared preliminary data suggesting that their experimental vaccines can protect older adults and newborn infants from the virus.
Use of the drugs in children under the age of two was associated with lower antibody levels after the jabs—perhaps, researchers suggest, due to microbiome alterations.