Nahid Bhadelia is an infectious diseases physician and founding director of Center for Emerging Infectious Diseases Policy and Research at Boston University.
We cannot let this persist. Health officials — and the public at large — must shore up our defenses against all diseases and keep routine childhood vaccination requirements from becoming enmeshed in our growing ideological divide.
All vaccines work in two ways: First, they build immune memory to help protect against infectious diseases and reduce our ability to transmit them. Second, they reduce the chance we come across anyone else with the disease through the same mechanism (particularly important for vulnerable people, such as the elderly or immunocompromised). That means vaccines work best when they have high rates of population uptake.
Should population immunity wane against a disease (for example, if people start refusing to be vaccinated or having their children vaccinated against diseases such as measles, diphtheria or polio), more of that infectious disease is likely to circulate. Because no vaccine is 100 percent effective, that means breakthrough infections are possible even among those who are healthy. The percentage of vaccinated required depends on the disease, with highly transmissible diseases such as measles requiring more than 95 percent; for polio, it’s closer to 80 percent.
Vaccine hesitancy was already a top global health threat before the pandemic, as the World Health Organization warned in 2019. Measles cases had increased by 50 percent worldwide between 2015 and 2019. The United States, which had eliminated the disease in 2000 with widespread childhood requirements and rapid public health, reported nearly 1,300 cases in 2019, 88 percent of them in close-knit, under-immunized communities.
This is because parents in some areas of the country have increasingly sought non-medical exemptions to vaccine requirements in the past decade. The worst measles outbreaks — in California, New York and Minnesota — all took place as a result of aggressive anti-vaccination campaigns.
The covid-19 pandemic supercharged this movement, providing fertile ground for anti-vaccine advocates as well as politically driven, state-sponsored disinformation actors. Perhaps one of the most concerning trends is the alignment of vaccine uptake with political ideology. The red-blue political gap has persisted, with 90 percent of Democrats saying they will vaccinate their children for covid-19, compared to 19 percent of Republicans. Seventeen states have banned student coronavirus vaccine mandates, even though all 50 states already mandate some of the 16 Centers for Disease Control and Prevention recommended vaccines for K-12 students.
Anti-coronavirus vaccine sentiments may be bleeding into an erosion of support for all routine childhood vaccinations. Last year, a YouGov poll showed a 13 percentage point decline among Republicans regarding support for childhood vaccines (from 59 percent to 46 percent). Some states, such as Montana and Nebraska, have either passed new legislation or are working to pass bills to make it easier to get exemptions from childhood vaccine requirements. Many of these states, such as Texas, are home to counties that were already at risk before the pandemic because of clustered unvaccinated populations.
On top of this, epidemics often lead to a drop in immunizations for other diseases because of the disruption in health services. As an outbreak responder, I witnessed the impact that the Ebola epidemic had on the incidence of new outbreaks in West Africa from vaccine-preventable diseases. The covid-19 pandemic has had an exponentially larger impact globally. In July, WHO reported that more than 23 million children worldwide missed out on routine immunizations in 2020.
Even more alarmingly, in many parts of the world, overwhelmed health-care systems have led to a decline in the detection of new infections. The longer the pandemic continues, the larger the gaps in routine vaccine coverage and disease detection will become. In the United States, a CDC study reported drastic drops in childhood immunizations in 10 jurisdictions during the spring of 2020, and although there was an increase in vaccinations after the first wave of the pandemic, by that fall, the rates of vaccination were still not high enough to match prior years, leading organizations to urge “catch up” shots to avert outbreaks.
What can be done? First, we must support routine childhood vaccination regardless of our political affiliations. The health of our communities and our economy depends on ensuring that we maintain a high level of immunity to diseases we have already defeated. Having worked as an infectious diseases physician in resource limited settings, I know how infectious diseases can drive people into the disease poverty traps. We cannot let it worsen globally or take hold here.
Lastly, clinicians must be more vigilant about detecting vaccine-preventable diseases that might appear in our clinics with greater frequency. Parents should talk to their pediatricians if they have questions about childhood immunizations in a safe space where they can receive reliable information.