The danger of delaying vaccination

Last week, the Maryland Department of Health reported a 15 percent increase in the number of confirmed or probable pertussis cases in the first half of this year, compared to 2016. Pertussis — also known as whooping cough — is a highly contagious respiratory disease that can cause serious illness and even death. The observed increase in this preventable disease in Maryland should stand as a stern warning to any parent who is considering skipping the pertussis vaccine for their child — or delaying it. Immunizing our children against serious infectious diseases, and doing so in a timely manner, are both critically important to ensuring public health.

One of the confirmed pertussis cases in Maryland this year involved a 7-month-old whom health officials described as “slightly delayed in immunizations.” On-time vaccination for pertussis is particularly important for infants and young children because the disease is more likely to cause serious and sometimes deadly complications in this population.

Unfortunately, as the number of available childhood vaccines increases, many parents are opting to spread out vaccine administration in a mistaken belief that it’s somehow safer than following the Centers for Disease Control and Prevention’s recommended vaccination schedule. It’s not. One study, for example, found no difference in neuropsychological outcomes among 7 to 10 year olds who received on-time vaccine delivery in their first year compared to children of the same age whose parents delayed some vaccines until after their child’s first birthday.

Despite this and other evidence, the percentage of parents who intentionally delayed their children’s vaccinations is holding steady, according to a national survey. This should give public health officials and health care workers pause. Clearly, targeted communication strategies and additional education are needed nationwide to dispel myths about vaccines and to encourage timely vaccination.

Over the years the medical and public health communities have worked hard to increase childhood vaccination rates overall, and there are indications their efforts are working. The same national survey found that the percentage of parents who refused for their children one or more vaccinations has declined significantly, from 5.4 percent in 2012 to 3.6 percent in 2014. According to the study authors, this decline in vaccine hesitancy “may be reflective of more vigorous vaccine promotion at the state level in recent years to decrease use of nonmedical philosophical and religious exemptions.” For example, California saw the highest vaccination rate among kindergartners since 1998 last fall after implementing a new law that eliminated religious and personal belief vaccine exemptions.

This progress is encouraging, but there is still work to do. While some of them are hesitant to vaccinate their children for religious, moral or philosophical beliefs, too many others shun vaccines over a fear of adverse side effects, despite overwhelming evidence of the safety and efficacy of immunizations and consensus in the medical community.

Vaccine refusal has been associated with numerous infectious disease cases and outbreaks in the United States, among them that rising incidence of pertussis, which includes successive epidemics with an epidemiology similar to those in the pre-vaccine era. Yes, waning immunity in older vaccinated individuals is thought to be one contributor. But recent large outbreaks of pertussis — in Arizona in 1988, California in 2010 and 2014, Washington in 2012, and Oregon in 2012 — included a large number of children who were unvaccinated or undervaccinated (i.e., those who have received fewer than the recommended dose of vaccine).

The CDC recommends more than a dozen vaccines for children from birth through age 6, including DTaP, which prevents diphtheria, tetanus and pertussis. It is paramount that parents adhere to CDC’s recommended schedule for vaccinations to protect all children, including those who are unable to receive vaccinations (e.g., due to allergies or compromised immune systems) and thus must rely on herd immunity for protection.

Maryland officials are urging parents to vaccinate their children before the start of the 2017-18 school year. When students return in the coming weeks, there will be prime opportunities for pertussis and other infectious diseases to spread in the close quarters of classrooms across our state and our nation. Parents, take this important step to ensure the health of your child and those around them. Don’t delay.

Diane Meyer (dmeyer10@jhmi.edu) Jennifer Nuzzo (jnuzzo1@jhu.edu) and Matthew Shearer (mshearer@jhu.edu) are faculty members at the Johns Hopkins Center for Health Security at the Johns Hopkins Bloomberg School of Public Health and members of the Outbreak Observatory project team.

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