Vaccination campaigns like this one held in February in Monrovia, Liberia can help close the vaccination gap caused by the Ebola epidemic in West Africa. | UNMEER/ CC BY-ND 2.0
Countries hit hardest by the ongoing Ebola outbreak in West Africa could face a second public health disaster if efforts to vaccinate children against measles and other vaccine-preventable infections are not resumed quickly and carefully, researchers warn.
Infections such as tuberculosis, diphtheria, and pertussis — but especially measles — are poised to claim as many lives as Ebola has in Liberia, Sierra Leone, and Guinea unless gaps in the nations' vaccination campaigns left in the wake of Ebola are filled, they say.
Saki Takahashi from Princeton University in the United States, along with American and European colleagues, analyzed data on the number of West African children who were unvaccinated against measles before the Ebola-related healthcare disruptions began. They then accounted for a 75% reduction in routine vaccination rates in order to estimate the increasing risk of measles and other infections related to the ongoing Ebola crisis.
"Even a 25% reduction [in routine measles vaccination rates] would be expected to result in tens of thousands of additional cases and between 500 to 4,000 additional deaths," said Justin Lessler, a co-author of the Science report, during an 11 March press teleconference.
"Supplemental immunization campaigns have been successfully performed in all three countries in the past," Lessler added, "and they could virtually eliminate Ebola's effect on measles risk in the region, likely making the situation better than it was before the Ebola crisis began."
The researchers' findings are published in the 12 March issue of the journal Science.
Compared to other vaccine-preventable diseases, measles is particularly contagious, and outbreaks of the infection have been known to follow humanitarian crises. Measles vaccination rates also tend to be a bit lower than other vaccination rates, according to the researchers, because the vaccine can't be given right after birth.
"This combination of factors means that measles is one of the first [infections] in the door when anything happens — whether it's political unrest, a crisis like Ebola, or a natural disaster — that causes vaccine rates to go down," explained Lessler.
Ebola-related healthcare disruptions can increase the risk of a measles outbreak in West Africa. (View larger image) | Justin Lessler and Saki Takahashi
Before the 2014 Ebola outbreak in West Africa, when vaccination efforts were in place, a regional measles outbreak among unvaccinated children in these countries would have caused about 127,000 infections, according to the researchers. But if there were 18 months of healthcare delays and disruptions related to Ebola, the number of measles cases caused by a concurrent outbreak could jump to 227,000 and result in between 2,000 and 16,000 additional measles-related deaths.
"We estimated that, prior to the Ebola outbreak, there would be 7,000 deaths due to measles," said Takahashi during the teleconference. "Then we estimated that, after 18 months of Ebola-related healthcare disruptions, there would be about 12,000 deaths due to measles."
"For every month that disruptions continue and that no campaign is conducted to fill the existing holes in measles immunity, the risk of both an outbreak occurring and the impact of such an outbreak increases," added Lessler. "If [vaccination] campaigns reached levels of coverage that have been reached during previous campaigns in the region, we could expect that the risk of a measles outbreak would be far less than it was before the Ebola crisis happened."
"All three countries — Liberia, Sierra Leone, and Guinea — had been considering vaccination campaigns before the Ebola crisis occurred, but these campaigns were delayed by the Ebola crisis," he said.
The researchers' bottom line is clear: To thwart a second public health disaster, public health officials in West Africa should conduct supplemental vaccination campaigns for children as soon as it is safe to do so.
"Vaccination campaigns strive to reach children that haven't been reached by routine immunization services and, clearly, this will still hold true," said Takahashi. "However, we would suggest that a bundle of vaccines be included in such a campaign — not just for measles, but also for DTP (diphtheria, pertussis, and tetanus), polio, pentavalent vaccine — and if possible, perhaps coupled with other public health interventions, including vitamin A supplementation…as well as things like bed nets and anti-malarial drugs."