Johns Hopkins Bloomberg School of Public Health researchers say that major disruptions in the health care systems in West Africa caused by the Ebola crisis have led to significant decreases in vaccinations for childhood diseases, increasing susceptibility to measles and other vaccine-preventable illnesses.
Should a large measles outbreak occur in the region, nearly twice as many people could be sickened by the disease and thousands more could die, the researchers report in the March 13 issue of Science. For every month of interruption in the health care system, they say, an additional 20,000 children between the ages of nine months and five years become susceptible to the measles.
"The secondary effects of Ebola - both in childhood infections and other health outcomes - are potentially as devastating in terms of loss of life as the disease itself," says study leader Justin Lessler, PhD, an assistant professor in the Department of Epidemiology at the Johns Hopkins Bloomberg School of Public Health. "While the downstream effects of Ebola are many, we can actually do something about measles relatively cheaply and easily, saving many lives by restarting derailed vaccination campaigns."
The current Ebola outbreak began in December 2013 in Guinea and since then there have been more than 14,200 confirmed cases in Guinea, Liberia and Sierra Leone, with more than 9,500 deaths blamed on the disease in those nations. Many health-care facilities in the region have been closed; many citizens have stayed away from those that are open for fear of contracting the deadly disease. As a result, many have not received routine medical care.
Measles epidemics often follow humanitarian crises, Lessler says. Measles, one of the most transmissible infections, tends to have lower vaccination rates in many developing countries, partly because the vaccine is given around nine months of age, when parents may no longer have regular contact with health care providers. But over the past decade, successful vaccine campaigns have led to dramatic drops in the number of measles cases in the region.
For their new research, Lessler and his colleagues used data-driven models of the region to estimate potential measles outbreak risk, attack rates and mortality rates resulting from a 75-percent disruption in health care services in West Africa stemming from the Ebola outbreak. They also looked at 25, 50 and 100 percent reductions, but 75 percent was most in line with reports available at the time. (Recent reports suggest smaller, but still severe, disruptions). Their 18-month forecasts are based on geospatial mapping as well as the projection of age-related patterns of susceptibility to the measles.
The researchers estimated that prior to this Ebola outbreak there were about 778,000 children between nine months and five years old in the three nations who had not been vaccinated against measles, equating to roughly 4 percent of the population. After 18 months of Ebola-related disruptions to the health-care system, the researchers estimate, there will be up to 1,129,000 unvaccinated children between the ages of nine months and five years, a 45 percent increase.
In the event of a large regional measles outbreak, the number of estimated cases was roughly 127,000 before Ebola and, after 18 months of interruption, an additional 100,000 cases would be estimated to occur. The lion's share of these cases would likely be in young children who are at greater risk of complications. The researchers estimate that between 2,000 and 16,000 additional measles deaths could occur in such an outbreak.
While Lessler and his colleagues only looked at the potential for a measles outbreak, he says the Ebola epidemic has also slowed delivery of the oral polio vaccine, a tuberculosis vaccine and the pentavalent vaccine, which protects against Haemophilus influenzae type b (the bacteria that causes meningitis, pneumonia and otitis), whooping cough (or pertussis), tetanus, hepatitis B and diphtheria. He estimates that the number of children not receiving these vaccines in the region may be 600,000 to 700,000. The provision of health care to people with malaria, HIV and tuberculosis has also been disrupted.
"These setbacks have the potential to erode the substantial gains in the control of these diseases over recent decades," Lessler says. "It could be a long time before the health care systems in the region recover from this."
Lessler says he hopes that with a better understanding of the scope of the measles susceptibility problem, governments and non-governmental organizations will be able to focus their resources on restarting vaccination programs in order to mitigate the side effects of the Ebola crisis.
"Reduced vaccination and the risk of measles and other childhood vaccinations post-Ebola" was written by Saki Takahashi, C. Jessica Metcalf, Matthew J. Ferrari, William J. Moss, Shaun A. Truelove, Andrew J. Tatem, Bryan T. Grenfell and Justin Lessler.
The research was supported by a grant from the Bill & Melinda Gates Foundation; a contract from the U.S. Department of Homeland Security Science & Technology Directorate; the RAPIDD program of the Department of Homeland Security Science & Technology Directorate; the National Institutes of Health's Fogarty International Center; and the NIH's National Institute of Allergy and Infectious Diseases (R01 AI102939 and U19AI89674).