In the early 1800s, Edward Jenner showed he could protect children from smallpox if he infected them with lymph from a cowpox blister.

This led to the first use of vaccines to protect public health. It also led to the start of the anti-vaccination movement.

Over two centuries, the proponents of immunization and the practice’s critics have grown together, with scientists finding ways to stop the spread of communicable diseases while a vocal minority of skeptics challenges them at every step.

The grounds for their objections change over time, but they generally boil down to a lack of trust in government officials and the medical establishment. They question whether a relatively small number of negative vaccine reactions are worth the benefits of near universal immunity.

But at the same time, scientific evidence has mounted showing that vaccination is strongly associated with suppressing the spread of disease.

Where there is more vaccination, there are fewer outbreaks; and where there is less vaccination, there are more. The New England Journal of Medicine mined records going back to 1924 and determined that vaccines prevented 100 million cases of infectious disease.

MAINE’S EXPERIMENT

Maine has run its own experiment on this question — unintentionally. Maine has one of the loosest vaccination regimes in the country, allowing parents to send unvaccinated children to school and day care centers if they express a “philosophical” objection.

As a result, Maine has some of the highest opt-out rates in the country. It also has some of the worst results when it comes to the spread of infectious disease.

A majority of legislators tried to do something about this in 2015 but were not able to get past a veto by then-Gov. Paul LePage. With a new governor and new lawmakers in Augusta, it’s time to eliminate nonmedical opt-outs for childhood vaccinations. A bill is currently being drafted to bring state law up to date.

Recent data should give proponents of tighter vaccine requirements something to work with. Maine’s rate of pertussis, or whooping cough, was the worst in the country in 2017, the last year in which data are available for state-by-state comparisons. At 27.7 cases per 100,000 of population, it was five times the national average, according to the U.S. Centers for Disease Control.

Last year, the number of pertussis cases increased in Maine from 410 in 2017 to 446, according to state data.

In the 2017-2018 school year, about 5 percent of incoming Maine kindergartners had nonmedical exemptions for immunizations, but they are not evenly distributed. Thirty-one public elementary schools were reporting 15 percent or higher unvaccinated rates, putting those schools and surrounding communities at greater risk.

The problem with letting people decide whether to vaccinate their children is that the people who choose not to vaccinate are not necessarily the people with the highest risk.

HERD IMMUNITY

People with suppressed immune systems, such as children with leukemia, cannot be vaccinated for medical reasons. They rely on herd immunity — where their exposure to a disease is minimized because most of the people around them are vaccinated. If an outbreak of a disease spreads though the unvaccinated community, people who aren’t vaccinated because they are already sick would have the most to lose.

Three states — California, Mississippi and West Virginia — allow only medical exemptions for children who are enrolled in public schools. The rule is called “forced vaccination” by some in the anti-vaccination community, but it’s not.

Families could still chose not to vaccinate their children, but they couldn’t send them to public school, where they would put vulnerable people at risk. No one can force them to vaccinate, but they should not be able to force exposure on people who can’t choose to protect themselves.

Few living Americans remember what it was like before vaccination was common. There were thousands of deaths every year from pertussis, diphtheria and polio. Today, there are virtually none.

We shouldn’t have to remember the epidemics to recognize that we are better off with vaccines. Maine law should get off the fence and end nonmedical exemptions for vaccination.