According to the Centers for Disease Control (CDC), as of April 24 there have been 844 confirmed cases of measles in the US in 2025; 11% of cases have resulted in hospitalization and 3 patients have died. The majority of cases (96%) have been in unvaccinated persons or in those whose vaccination history was unknown

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In the first six months of 1989, more than 7,000 cases of measles were reported to the US Centers for Disease Control (CDC), a sharp increase over previous years (Morbid Mortal Weekly Rep, 33:456, July 7, 1989). Many of these cases occurred in children and college students who had previously been vaccinated against the disease. Practitioners have asked, therefore, whether their previously immunized young patients should receive a second (or, in some cases, third) immunization against measles.

The CDC has reported that many states are experiencing a higher-than-usual incidence of pertussis this year. The highest incidence has been in infants, but the disease has also occurred in older children, adolescents, and adults. Thirteen pertussis-related deaths were reported through August 24; the majority of these were in infants <3 months old.

The FDA has restricted its Emergency Use Authorization for the adenovirus-based COVID-19 vaccine manufactured by Johnson & Johnson (Janssen) to adults who are unable or unwilling to receive another COVID-19 vaccine. The mRNA COVID-19 vaccines manufactured by Pfizer/BioNTech (Comirnaty) and Moderna (Spikevax) are preferred for all persons without a contraindication.

An outbreak of monkeypox has recently spread around the globe and across the US. Updated information about the current outbreak is available from the CDC.

A large mumps outbreak that began in Iowa in December 2005 has spread. About 40% of the cases have been in people 18-25 years old, many of whom are college students and had been vaccinated against the disease.

On June 25, 2021, the FDA added a warning to the Fact Sheets for the mRNA-based COVID-19 vaccines manufactured by Pfizer/BioNTech (Comirnaty) and Moderna (Spikevax) about an increased risk of myocarditis and pericarditis following administration of the vaccines.

The FDA has expanded its Emergency Use Authorizations (EUAs) for the mRNA COVID-19 vaccines manufactured by Pfizer/BioNTech (Comirnaty) and Moderna (Spikevax) to allow for their use in children as young as 6 months old. The Pfizer vaccine was previously authorized for use in persons ≥5 years old, and the Moderna vaccine was authorized for use in adults ≥18 years old.

Medical Letter consultants have brought to our attention some confusion that has accompanied the release of Adacel, a combination of tetanus toxoid, diphtheria toxoid and acellular pertussis antigens (Tdap) recently approved for use as a booster in adolescents and adults 11-64 years old (Med Lett Drugs Ther 2006; 48:5). Another Tdap vaccine, Boostrix, is approved for use in adolescents 10-18 years old. Some adults have inadvertently been immunized with Daptacel or Infanrix (DTaP), which are intended for active immunization of infants and children 6 weeks to 6 years old. Such mix-ups were...