Measles Jumps From Unvaccinated Children to Unvaccinated Adults

Nancy A. Melville

May 24, 2012

May 24, 2012 (Thessaloniki, Greece) — The details of a measles outbreak in one region of France, which started in unvaccinated children in 2008 and shifted to unvaccinated adults by 2011, offers a snapshot of an epidemic in progress, and might provide lessons on the potential fallout from an inadequately vaccinated population.

In research presented here at the European Society for Paediatric Infectious Diseases 30th Annual Meeting, Henri Laurichesse, MD, from CHU Clermont-Ferrand, Service des Maladies Infectieuses et Tropicales, in France, described how the outbreak, in the south-central region of Auvergne, got started and was able to quickly make its way into unvaccinated pockets of the community.

"The outbreak started with a few cases in traveling [gypsy] communities in 2008, and then outbreaks in families of unvaccinated children were reported," said Dr. Laurichesse.

"This was followed by school clusters, and then the disease evolved into a community-wide outbreak, which included young adults, by May 2011."

The outbreak was part of a much larger outbreak in Europe, which involved more than 37,000 cases of measles in 2011 alone, and included 27 cases of measles encephalitis, with the potential for permanent neurologic sequelae, and 8 measles-related deaths, according to the World Health Organization.

There were approximately 14,000 measles cases in France in 2011 — a country that before 2008 had only a few dozen cases per year.

In total, the regional outbreak in Auvergne involved 376 cases —160 children (42.6%) and 216 adults (57.4%). The median age of the adults was 26.7 years; 113 (52%) adults were referred to the university hospital and 71 (63%) were hospitalized.

Pneumonia was confirmed in 31 patients, diarrhea occurred in 29, biological hepatitis in 47, and thrombopenia in 39.

"We were surprised to have so many cases of diarrhea and viral hepatitis associated with measles, and we had very frequent thrombopenia," Dr. Laurichesse said.

There was 1 case of encephalitis that required intensive care; however, no deaths were reported in the regional outbreak.

Thirty of the cases (27%) had previous exposure, and secondary cases occurred in 18 patients (16%). Nineteen of the cases occurred among unvaccinated healthcare workers; only 5 of those cases were hospital-acquired.

Of 110 cases, 92 involved unvaccinated patients and 18 of the 110 (16%) had received 1 dose of the measles, mumps, and rubella (MMR) vaccine.

Unvaccinated patients had a significantly higher rate of hospitalization (= .005) and complications.

"The results indicate that most of the cases were unvaccinated, while a low proportion had 1 dose of MMR," Dr. Laurichesse said. "When we looked at complications, we found the unvaccinated patients were more likely to be hospitalized and to have pneumonia."

"What we have learned from this study focused on adults is that the vaccine coverage in our region explains the spread in our community," Dr. Laurichesse said. "Many of the adults who were not immunized were born close to the year when France introduced MMR, so that may explain some of the cases."

The vaccine coverage rate among children in the region is greater than 85%; however, most children are vaccinated with just 1 dose. In the United States, most children receive a first MMR vaccine at 12 to 15 months of age, followed by a second dose at 4 to 6 years of age.

According to James D. Cherry, MD, MSc, professor of pediatrics at the David Geffen School of Medicine at the University of California at Los Angeles and Mattel Children's Hospital, 1 dose simply might not be enough.

"In studying the recurrence of measles, we learned 40 years ago that 1 dose of vaccine would not be enough, so we suggested a 2-dose schedule in the United States," said Dr. Cherry.

"It took 17 years to accomplish that, but we've been measles-free, with the exception of importations, for 12 years now."

"People have to realize that you need 2 doses of vaccine — not as a booster dose, but to seroconvert those who don't seroconvert the first time."

A bigger challenge, however, might be in convincing some families and practitioners to get even 1 dose, said Ronald de Groot, MD, PhD, from the division of pediatric infectious diseases at Radboud University Nijmegen Medical Centre in the Netherlands.

"The problem with measles in France is the result of a failure to have an adequate [more than 95%] vaccination rate against measles, caused by substantial groups of parents who do not want to vaccinate their children," Dr. de Groot said.

For many parents, the resistance stems from concerns about vaccine safety. Despite an absence of credible evidence on health risks related to the MMR vaccine, several prominent vaccine opponents continue to fuel the unfounded concerns.

"There are a number of pseudoimmunologists, particularly in Germany, Switzerland, and Austria, who are basically against vaccines; these countries do not have mandatory vaccination policies," Dr. Cherry said.

"They will never get rid of measles unless they do something about getting this cohort of people immunized. They need to immunize more than 90% of the population [who have not had measles] with 2 doses of vaccine."

In an effort to address the problem, France has initiated a nationwide campaign to raise awareness about the need for MMR vaccination.

Dr. Laurichesse and Dr. Cherry have disclosed no relevant financial relationships.

European Society for Paediatric Infectious Diseases (ESPID) 30th Annual Meeting. Presented May 10, 2012.

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