Vaccinations and outbreaks

May 8th, 2019

What are vaccinations?

To vaccinate or not to vaccinate — in recent years this has become one of the key questions many new parents are asking themselves. However, even though vaccines are a topic of fierce and contentious debate, many people don’t understand how vaccines work, and others mistrust the science behind them.

Vaccinations have been around since the 1790s. Edward Jenner, often called the “father of immunology,” was a surgeon who noticed that milkmaids exposed to cowpox seemed to be immune to smallpox. Out of this observation, he developed a smallpox vaccine from the less aggressive cowpox that went on to save countless lives.

At their most basic, vaccines function by triggering antibodies. When you’re given a vaccine, you’re receiving a dead or weakened form of the virus or bacteria that you are being vaccinated against. In response, your immune system produces antibodies that are prepared to fight off the disease. So if at some point you’re exposed to a stronger form of the disease in the future, your immune system remembers how to make the antibodies and can respond immediately.

This is particularly important for diseases like measles and whooping cough, which can attack the body so quickly that the immune system doesn’t have time to respond normally before being overwhelmed. Children under five years old and adults with weakened immune systems are especially vulnerable to these quick strike diseases. Pre-exposure via vaccine means that the immune system can respond immediately rather than waiting for antibodies to develop.

The flu vaccine works in a slightly different way, as there are often several strains of influenza at any given time. Each year, researchers work to create a vaccine “match” that works against the most likely flu strains. However, because there are various types of the flu virus, you can receive the flu vaccine yet still become infected with a strain of the flu that you haven’t been vaccinated against. 

The return of childhood illness

In the year 2000, the United States declared that measles had been eliminated from the country, approximately 40 years after the introduction of a widespread vaccine in 1963. Before the vaccine, there had been more than four million cases of measles every year, resulting in an average of 48,000 hospitalizations and over 500 deaths. The elimination of the disease was achieved by way of “herd immunity,” a term used when a high enough percentage of the population has been vaccinated that the disease no longer spreads even to those who aren’t vaccinated. For measles, herd immunity is usually achieved once 90–95 percent of a population is vaccinated.

However, as more parents have chosen not to vaccinate their children, measles and other childhood diseases deemed eliminated have begun to reemerge with increased frequency. In 2014, the United States reported the largest outbreak of measles since 2000, with 667 cases. As of April 26, 2019, the Centers for Disease Control and Prevention (CDC), which updates its data weekly, reported that there have been 704 confirmed cases of the disease this year — more than the whole of 2018 (which was 372).

An ongoing measles outbreak in Washington State recently prompted Governor Jay Inslee to declare a public health emergency. Measles is highly contagious, and the disease can incubate in carriers for 10–12 days before they show symptoms. A carrier of measles can infect 12–18 others without knowing it. Early symptoms are similar to a cold — fever, runny nose and cough — which are then followed by a telltale red rash. Measles is an airborne virus that can linger in the air after an infected person has coughed, and the virus can survive on surfaces for up to two hours after initial exposure.

Measles presents a number of additional risks to those who contract it, the most common of which is pneumonia. The disease has also been known to lead to diarrhea, mouth ulcers and even blindness. In severe cases, encephalitis (swelling of the brain) can occur, resulting in convulsions, intellectual disabilities and even death. Fortunately these complications are rare, but they’re more likely to affect those with already compromised immune systems.

Responding to outbreaks

Outbreaks of measles and other childhood diseases often begin in tight-knit social groups where vaccination rates are relatively low. For instance, a current outbreak in Rockland County, north of New York City, began in an ultra-Orthodox Jewish community after travelers contracted the virus in Israel, which is experiencing a measles epidemic. From there, the virus began to spread to others in their community who were unvaccinated and then beyond into the wider population.

Rockland County recently responded by declaring a state of emergency that banned children who are unvaccinated from indoor public spaces such as schools, houses of worship and restaurants in an attempt to cut down on the spread of the virus. Local parents sued, saying the ban “ ‘achieves no valid public purpose’ and deprives children of their right to an education,” NPR reported. A state judge, who determined that a state-of-emergency declaration wasn’t warranted, blocked the ban. While the county’s effort isn’t a popular move, it’s indicative of public officials’ desire to contain the disease and keep it from spreading.

“Despite our best efforts, this outbreak is not going away,” Ed Day, Rockland County chief executive, said in a press conference in mid-April. “If anything, it is now accelerating, much as we feared. We have seen 33 new cases since we declared our now-nullified state of emergency three weeks ago. In short, we saw this coming.” The county continued its efforts to fight the growing measles outbreak by issuing a second, revised state of emergency for 30 days at the end of April.

Ogbonnaya Omenka, an assistant professor at Butler University, said in an interview with USA Today, “One of the most challenging aspects of public health is balancing between individual liberty, for people who don’t want the vaccine for whatever reason, and what is best for everyone.”


Herd immunity

Herd immunity is a term used in immunology to describe the threshold that must be met for a population to be considered “immune,” or protected, from a disease. Herd immunity is particularly important as an indicator for the safety of those who have compromised immune systems or who cannot receive vaccinations (such as a child with a chronic illness). For measles, a highly contagious disease, herd immunity is reached at an immunization rate of at least 90–95 percent of the population. However, herd immunity doesn’t work for all diseases. Tetanus, for example, isn’t spread person-to-person and therefore cannot be protected against through herd immunity.

The Green Meadow Waldorf School in Rockland County, New York, in complying with a county health department order for schools that had vaccination rates lower than 95 percent, has implemented major restrictions for its students who are unvaccinated. More than 40 students have been banned from attending school until they’re vaccinated, a March 14, 2019, Washington Post article reports. In December 2018, the school had a vaccination rate of just 33 percent, far below the necessary 95 percent threshold. In order to prevent the spread of a measles outbreak in an area below the herd immunity threshold, containment is often the best option.

“While no one enjoys the fact that these kids are out of school, these orders have worked,” Thomas Humbach, the county’s attorney, is quoted in the Post article as saying. “They have helped prevent the measles outbreak from spreading to this school population.”

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