(NewsNation) — Florida’s top health official is defying quarantine recommendations for unvaccinated people during a measles outbreak at a school in Weston, Florida.

Dr. Joseph A. Ladapo, Florida’s surgeon general, acknowledged the “normal” recommendation for a 21-day quarantine in a letter to parents but said the state was leaving it up to parents and guardians to determine whether their children should continue to attend school. The letter did not tell parents they should have their children vaccinated.

Though measles is officially considered eliminated in the U.S. measles outbreaks have been popping up as more people fail to vaccinate their children.

Six cases of measles were reported in Broward County, Florida, and the state’s 90.6% kindergarten vaccination rate is too low to guarantee herd immunity. Those who are unvaccinated and born after 1957 are vulnerable as are babies, since the first dose of the Measles, Mumps and Rubella (MMR) vaccine isn’t given until 12-15 months. People born before 1957 are considered immune through exposure to the disease before the vaccine was available.

Measles is extremely contagious and difficult to track exposure because of how the disease spreads. People are contagious four days before and four days after a rash appears and the incubation period ranges from seven to 21 days from exposure. Measles particles can also linger in the air or on surfaces for up to two hours, potentially infecting others.

Because it is so contagious, 90% of unvaccinated people who are exposed to measles will contract the disease. Children in a classroom with an infected child are considered exposed, even if they have not had direct or close contact with the patient.

Symptoms of measles include a cough, runny nose, red and watery eyes, a high fever, lethargy, greyish-white spots in the mouth and the disease’s characteristic blotchy, red-brown rash.

In addition to being extremely contagious, measles is also a serious illness. One in five people with measles will be hospitalized, one in 10 can have permanent hearing loss from ear infections and one in 1,000 die from respiratory or neurological complications.

Measles may also cause immune amnesia, wiping out the body’s memory of past infections and making people vulnerable to illnesses they have already had and developed immunity to.

The severity and high rate of contagion of measles is why the Centers for Disease Control and Prevention recommends that unvaccinated people who are exposed quarantine for 21 days to prevent outbreaks from spreading.

Ladapo has gone against established public health recommendations before. He went against CDC recommendations for vaccinations, cast doubt on the efficacy of the COVID-19 vaccine and called for a stop to mRNA vaccines, citing debunked claims about the shot.

Ladapo has also been accused of misleading the public through op-ed articles that argued against lockdowns and masking during the COVID-19 pandemic.