Measles was declared eliminated from the US in 2000 thanks to high vaccination rates. But amid misinformation from anti-vaccine activists—including current US Health Secretary Robert F. Kennedy Jr.—vaccination rates have continuously slipped in recent years, vaccination exemptions have hit an all-time high, and the highly infectious virus has come roaring back.

The Centers for Disease Control and Prevention has tallied at least 3,659 cases this year, a tally higher than last year’s and the highest on record since 1991. Still, under the influence of Kennedy, the CDC has resisted reporting the deaths in Pennsylvania, instead altering the criteria for what it counts as a measles death. Currently, the CDC is reporting only two deaths. It’s unclear which two have been counted.

Meanwhile, health officials in Pennsylvania are racing to vaccinate residents amid the deadly outbreak. The health department reports that state nurses have administered more than 8,500 doses of measles, mumps, and rubella (MMR) vaccine this year, including more than 5,500 doses given at pop-up clinics in outbreak areas.

“The best protection against measles remains getting fully vaccinated,” the health department reiterated Wednesday. “The MMR vaccine, administered over two doses, boosts a person’s immune system and provides 97 percent lifetime protection.”