On Tuesday, the New York City Department of Health announced a public health emergency due to a 250-person measles outbreak in Williamsburg, Brooklyn.

In January, another measles outbreak in the Pacific Northwest sickened at least 74 people.

So far, nearly every child who has gotten ill is unvaccinated.

Vaccination rates have plummeted in pockets of the Pacific Northwest in recent years, as lies about the dangers of vaccines have spread.

The measles vaccine is safe for almost everyone and can prevent debilitating illness and death.

On April 9, the New York City Department of Health announced a public health emergency due to a measles outbreak in Williamsburg, Brooklyn. Since 2018, 250 people in the neighborhood have been infected with the disease and that number is till increasing, according to the press release.

As a result, Williamsburg residents in specific zip codes must get the measles vaccines immediately if they are not already vaccinated. If they don't do so within 48 hours and cannot prove vaccine exemption, the city has the right to fine them.

According to the New York Times, the majority of the 285 recent New York City measles cases have been concentrated in Hasidic communities in Williamsburg and Borough Park, where large groups of children are unvaccinated.

In January 2019, a similar public health emergency unfolded in the Pacific Northwest, when a measles outbreak sickened numerous people in Clark County, Washington, along with a man from the Seattle area and someone in Oregon. As of now, there are 74 confirmed cases in the region.

Both outbreaks were preventable.

In the Pacific Northwest, nearly all of the patients whose immunization status was confirmed didn't get their measles vaccination. One child who contracted the measles had gotten a single dose of MMR vaccine (the full course is two shots), which is about 93% effective at preventing the measles.

It wasn't always this way. State records in Washington show that during the 2004-05 school year, vaccination rates for kindergartners in Clark County were above 91%. But during the 2017-18 school year, Clark County youngsters entering kindergarten had an immunization rate of 76.5%.

In that 2004-05 school year, the vaccination rate was "getting close" to a threshold for herd immunity (around 95%), the Clark County public health director, Alan Melnick, told Business Insider.

Herd immunity is a level of vaccination at which people who can't safely get vaccines (because they have HIV, cancer, or other conditions which make their immune systems more fragile) are protected. When enough people around them are immunized, they can live within a kind of protective tribe of disease-free people and are thus relatively "immune" to illnesses like measles.

Opposition to vaccines is generally based on junk science that has been endorsed by celebrities like Jenny McCarthy who, with Oprah Winfrey's help, have falsely said there may be something dangerous about the measles vaccine. Melnick said one need look no further than his county's official Facebook page to glimpse the rampant (and at times sophisticated) anti-vaccine propaganda spreading around the area.

Here are just a few of the ripest examples.