Immunizations have protected generations of Americans from various communicable diseases that have historically wrought havoc.

Immunizations have proven to be so effective against various diseases such as measles, mumps and pertussis, that public schools systems around the country have mandates regarding student vaccinations. Allegheny County schools have about a 95 percent participation rate for vaccinations, which healthcare officials say is critical when it comes to protecting the population against widespread outbreaks. Mass immunizations, known as herd immunizations, follow the theory that if enough people are immunized against a disease, the majority of the population will be protected and the disease will not spread, Dr. Kristen Mertz, medical epidemiologist at the Allegheny County Health Department says.

While schools do have immunization requirements, there are exceptions to the rule, including objections to immunizations over religious, philosophical or medical reasons.

By the time they reach kindergarten-age, most children have been immunized against a wide variety of illnesses, Colleen Barcaskey, a nurse in the Avonworth School District says. While the healthcare workers in the district respect decisions to not vaccinate, Barcaskey says a part of their mission is to provide information on the importance of preventative medicine.

“There are families who choose not to immunize their children for a variety of reasons,” Barcaskey says. “We’re all aware of the media coverage about the emergence of all the diseases we thought were eradicated through vaccination.”

The past few years have seen reports of various disease outbreaks such as measles and mumps in areas across the country. According to the U.S. Centers for Disease Control, 61 cases of measles were recorded across 10 states — California, Florida, Michigan, Minnesota, Nebraska, New Jersey, New York, Pennsylvania, Utah and Washington — in the first four months of 2017. The majority of people who got measles were unvaccinated, the CDC says.

As for the mumps, from Jan. 1 to April 22, 2017, 42 states and the District of Columbia reported 2,570 cases. According to the CDC’s website, since the pre-vaccine era there has been more than a 99 percent decrease in mumps cases in the U.S.

Mara Alterior, also an Avonworth school district nurse, says those CDC figures, among other reports, highlight the importance of herd immunity.

“If we don’t have the right percentage of people to equal out the herd immunity, we’ll have increasing cases of preventable diseases,” Alterior says. “Some kids aren’t able to get the vaccines due to medical issues, so it’s important that we have the community immunity to go along with the personal aspect.”

Although Alterior and Barcaskey say it’s important to respect the beliefs of those who object to vaccinations, immunizations are an important community health protection. Alterior says many people who object might not understand what an outbreak of the disease can do and how it can affect people.

“With immunizations we are in a safer spot,” Barcaskey says. “We’d like to get to the point that we don’t have to worry about diseases that have been eradicated. The proven way we’ve been able to do that is through immunizations.”

Even if an infant has been vaccinated, that doesn’t mean the drug’s efficacy lasts a lifetime. Mertz says some vaccinations can wane over time, such as the pertussis vaccine. In 2012 and 2014 there were pertussis outbreaks in Allegheny County and most of the children who came down with the illness were vaccinated, she says. Barcaskey agrees, saying there are still some unknowns about the efficacy of vaccines and how long those issued during infancy and youth will last in the body. Eventually data will show if those vaccines last until people are in their 50s or 60s.

“There are always improvements to the vaccines, just like we are always looking at ways to improve health care delivery in all areas,” Barcaskey says. “We have found success with herd immunity. It’s not perfect. No part of health care is, but it’s better than it was.”