(Reuters Health) - Just a 5 percent decline in measles vaccination rates could triple the number of young children who get infected with the virus in the U.S., according to a study highlighting the risks of parents refusing to vaccinate their kids.
Nationwide, about 93 percent of children aged 2 to 11 years old get the measles vaccine, researchers note in JAMA Pediatrics. If this vaccination rate dropped to 88 percent, it could result in 150 additional measles cases a year and cost government health programs $2.1 million, not counting hospital bills, researchers estimate.
"Given increasing parental decisions to not vaccinate their children, we wanted to understand the effect of small reductions in vaccine coverage on overall measles cases," said study co-author Nathan Lo of Stanford University School of Medicine in California.
"We found that small declines in vaccine coverage can really reduce the 'herd immunity' effect and result in more frequent and larger outbreaks of measles," Lo said by email.
UNDATED: In this handout from the Centers for Disease Control and Prevention (CDC), a thin-section transmission electron micrograph (TEM) reveales the ultrastructural appearance of a single virus particle, or 'virion', of measles virus. in this undated image. Measles outbreaks have been reported throughout the U.S., with the latest reported February 5, 2015 at a daycare in suburban Chicago where as many as five children under the age of one have been infected. (Photo by CDC via Getty Images)
MILL VALLEY, CA - JANUARY 26: In this photo illustration, vials of measles, mumps and rubella vaccine are displayed on a counter at a Walgreens Pharmacy on January 26, 2015 in Mill Valley, California. An outbreak of measles in California has grown to 68 cases with 48 of the cases being linked to people who had visited Disneyland. Nine additional cases have been reported in five states and Mexico. (Photo by Illustration Justin Sullivan/Getty Images)
MIAMI, FL - JANUARY 28: Miami Children's Hospital pediatrician Dr. Amanda Porro, M.D prepares to administer a measles vaccination to a child at the Miami Children's Hospital on January 28, 2015 in Miami, Florida. A recent outbreak of measles has some doctors encouraging vaccination as the best way to prevent measles and its spread. (Photo by Joe Raedle/Getty Images)
1972: In this handout from the Centers for Disease Control and Prevention (CDC), a histopathology of measles pneumonia is seen in this microscope image from 1972. Measles outbreaks have been reported throughout the U.S., with the latest reported February 5, 2015 at a daycare in suburban Chicago where as many as five children under the age of one have been infected. (Photo by CDC via Getty Images)
MIAMI, FL - JANUARY 28: In this photo illustration, a bottle containing a measles vaccine is seen at the Miami Children's Hospital on January 28, 2015 in Miami, Florida. A recent outbreak of measles has some doctors encouraging vaccination as the best way to prevent measles and its spread. (Photo illustration by Joe Raedle/Getty Images)
A girl receives anti-measles vaccination drops at a health centre in BASECO compound in Tondo, Manila September 3, 2014. Philippine President Benigno Aquino said on September 1, 2014 between 11 to 13 million people in the country are at risk from measles, polio and rubella (German measles), and asked the public to cooperate in eradicating the preventable diseases, during Monday's launch of a mass national vaccination campaign against measles and polio, reported local media. REUTERS/Erik De Castro (PHILIPPINES - Tags: HEALTH SOCIETY)
A measles vaccine is seen at Venice Family Clinic in Los Angeles, California February 5, 2015. Lawmakers in several U.S. states are backing proposals to make it harder for parents to opt out of school vaccinations based on personal beliefs, as health officials fight a growing measles outbreak that has sickened more than 100 people in more than a dozen states. REUTERS/Lucy Nicholson (UNITED STATES - Tags: HEALTH POLITICS)
A girl looks on as a health officer injects her with measles vaccine at a school in Yemen's central province of Marib January 12, 2016. REUTERS/Ali Owidha
ACEH, INDONESIA - NOVEMBER 14: Students receive immunizations against TD (Tetanus Toxoid) and DT (Diphtheria Tetanus) during the implementation of the School Children Immunization Month in Lhokseumawe, on November 14, 2016 in Aceh, Indonesia.
TD immunization shots (Tetanus Toxoid) and DT (diphtheria tetanus) to prevent measles, diphtheria and tetanus, which aims to improve the health of students in Indonesia.
PHOTOGRAPH BY Fachrul Reza / Barcroft Images
London-T:+44 207 033 1031 E:firstname.lastname@example.org -
New York-T:+1 212 796 2458 E:email@example.com -
New Delhi-T:+91 11 4053 2429 E:firstname.lastname@example.org www.barcroftimages.com (Photo credit should read Fachrul Reza / Barcroft Images / Barcroft Media via Getty Images)
AMAZON, MANAUS, AMAZONAS STATE, BRAZIL - 2016/03/16: Measles, a highly contagious infection caused by the measles virus is an airborne disease which spreads easily through the coughs and sneezes of those infected - red rash which usually starts on the face and then spreads to the rest of the body is the typical symptom. Fundacao de Medicina Tropical do Amazonas ( Amazon Tropical Medicine Foundation ), Manaus city, Brazil. (Photo by Ricardo Funari/Brazil Photos/LightRocket via Getty Images)
Discover More Like This
BACK TO SLIDE
Measles is a highly contagious virus that can be serious or even fatal. It starts with a fever that can last a couple of days, followed by a cough, runny nose and pink eye. A rash develops on the face and neck then spreads to the rest of the body. In severe cases, pneumonia and encephalitis can develop.
People with measles can be spreading the virus for four days before and after the rash appears, according to the Centers for Disease Control and Prevention.
The virus can live for up to two hours on surfaces where an infected person coughs or sneezes. People can become infected by breathing in droplets or touching a contaminated surface and then touching their eyes, nose or mouth.
Because measles spreads so easily, about 95 percent of people need to be vaccinated against the virus to achieve so-called herd immunity, when outbreaks can be prevented, Lo said. Already, the nation is dotted with "hot spots" where vaccination rates are below this level and widespread outbreaks are possible, he added.
"Outbreaks happen in communities, so we need to zoom in further than just national or statewide statistics when it comes to vaccination rates," said Maimuna Majumder, a researcher at the Massachusetts Institute of Technology in Cambridge who wasn't involved in the study.
For example, one recent study in California found county-level measles vaccination rates as low as 70 percent even though the statewide average was 90 percent, Majumder said by email.
For the current study, Lo and co-author Dr. Peter Hotez of Baylor College of Medicine in Houston only examined data on measles vaccination and infection rates for children aged 2 to 11.
The estimated number of measles cases and associated costs would be much higher if the study also included infants, teens and adults, the authors note. Babies can't be vaccinated, and would be particularly vulnerable to infection if an older sibling caught the virus.
Very few people need to skip the measles vaccine for medical reasons, said Dr. George Rutherford, head of the division of infectious disease epidemiology at the University of California, San Francisco.
This includes pregnant women, patients with compromised immune systems related to conditions like cancer or AIDS and people who have had severe allergic reactions to vaccines in the past.
Even a small drop in vaccination rates can make it more likely that people who can't get the vaccine for medical reasons will catch measles, Rutherford, who wasn't involved in the study, said by email.
"When immunization levels go low enough, there can be massive outbreaks of measles," Rutherford said.
SOURCE: http://bit.ly/2utn13l JAMA Pediatrics, online July 24, 2017.