After almost 2 decades of progress, the global state of measles vaccination and measles mortality is deteriorating.
One of the most serious concerns of measles infection is its long-term neurological complications, including the fatal subacute sclerosing panencephalitis (SSPE) and measles inclusion-body encephalitis (MIBE), which is usually seen in immune deficient children. Although some efforts are being made to determine which patients might be most vulnerable to these outcomes, and to treat them, the best approach is still prevention and vaccination, according to Banu Anlar, MD, of Hacettepe University, Ankara, Turkey, who spoke during a session at the 2020 CNS-ICNA Conjoint Meeting, held virtually this year.
Worldwide vaccination strategies have slipped in recent years, leading to upticks in measles cases and vaccination rates. As a result, in 2018 the World Health Organization postponed its goal of eliminating measles by 2020. Future eradication goals will likely need to be modified, according to Anaita Udwadia Hegde MD, a pediatric neurologist in Mumbai, India, who also presented at the session.
After measles deaths dropped 74% between 2000 and 2010, coinciding with widespread increases in vaccination, the WHO felt emboldened to deal the disease a knockout blow. In 2010, it held a Global Technical Consultation to determine the feasibility of an eradication campaign, which concluded it should be possible by 2020. Several characteristics of measles made that a reasonable goal: It is passed only among humans, with no known animal reservoir; natural infection grants lifelong immunity; there is only one serotype; the virus is genetically stable; the vaccine is safe and leads to 95%-97% seroconversion after two doses, which provides long-term protection against known genotypes; the disease is easily recognized and tested for; and it had been successfully eliminated already in some regions of the world.
As of 2017, analyses showed that the vaccination program saved the lives of about 1.5 million children. That was a cause for celebration, but the goal of eradication has remained elusive. Vaccination rates have trailed targets. In 2018, UNICEF and WHO estimated that 86% of children globally received the first measles vaccine, unchanged from 2010 and below the goal of 95%. Only 69% of children received the second dose, below the goal of 80%. Four countries in Europe lost their measles elimination status in 2018.
Other attempts to eradicate diseases have met with mixed results. The only full success was smallpox, eliminated in 1977. Similar efforts with polio, malaria, guinea worm, and now measles have all come up short. Those failures could complicate future efforts because global agencies and donors may be leery of past failures because of potential harm to their reputations, according to Dr. Hegde.
Such programs require sustained financial commitment and political support as well as local trust. Nevertheless, they must continue for ethical reasons, said Dr. Hegde, but also for economic ones: Every $1 spent on vaccination programs saves $58 in future costs in low- and middle-income countries. Missed childhood vaccination also results in future vulnerable teenagers and young adults, and these populations are much harder to reach and can drive large outbreaks.
Several factors are contributing to the global regression in vaccine coverage, according to Kristen Feemster, MD, MPH, a pediatric infectious disease physician and the global director of medical affairs at Merck. Globalization has enabled the spread of the disease. Most cases in the United States are imported by travelers to countries where the disease is endemic. “Measles can happen anywhere in the world, and when it does it can travel and spread. If you have an unvaccinated traveler who is exposed to measles abroad, they can return home and spread it to anyone else who is unvaccinated or not otherwise immune. When we see cases they’ve been sporadic, but if you return to a community where immunization rates are low, you have the potential for more sustained spread,” Dr. Feemster said during her presentation.
Why are so many travelers unvaccinated? A key reason is that vaccine hesitance is growing. Most affected individuals involved in outbreaks are unvaccinated, usually by choice rather than for medical reasons. Concerns continue over the measles vaccine and autism, growing out of the debunked studies of Andrew Wakefield. In one example, a Somali community in Minnesota experienced a higher than usual number of autism cases and parents sought reasons to explain it. They discovered the supposed connection between vaccination and autism, and Wakefield himself met with a group of them. The result was a drop in vaccination and, in 2011 and 2017, sizable measles outbreaks.
2020 has of course brought a fresh challenge to measles vaccine with the COVID-19 pandemic, which has reduced access to health care and shifted scientific and health care interest away from measles and other vaccine-preventable diseases. On the positive side, social distancing, mask wearing, and restricted movement are likely reducing exposure to measles, but reduced vaccination rates are likely to result in future outbreaks. “There’s been a significant decrease in rates for routine immunizations globally, so there’s a potential for yet another resurgence of measles and other vaccine-preventable diseases,” said Dr. Feemster.
Dr. Feemster is an employee of Merck. Dr. Anlar and Dr. Hegde did not disclose any relevant financial relationships.