No Benefit in Delayed Immunization

By JENNIFER CORBETT DOOREN,

With young children receiving twice as many vaccines as they did 25 years ago, many parents are seeking to postpone at least some shots. A new study, though, finds no benefit to a child's development in delaying vaccines, and doctors warn that waiting can expose kids to possible disease.

One of the researchers, Michael J. Smith, a pediatric infectious-disease specialist at the University of Louisville School of Medicine in Kentucky, says some parents request alternative immunization schedules out of concern that getting so many vaccines in such a short time period might lead to health problems later on.

Dr. Smith and Charles R. Woods, also a pediatric infectious-disease specialist, looked at results of intelligence, speech and behavior tests conducted on children several years after receiving their infant vaccines and found few differences between children who were vaccinated on schedule and those who waited. "This study suggests that delaying vaccines does not give infants any advantage in terms of brain development," Dr. Smith said. Published online Monday in the medical journal Pediatrics, the study is believed to be the first to address the issue of delayed vaccination.



The study looked at data collected as part of the U.S. Vaccine Safety Datalink monitoring project, established in 1990 by the Centers for Disease Control and Prevention and eight managed- care organizations. The data originally were used in a study of the ingredient thimerosal and its effects on 42 tests measuring speech, language, intelligence, memory, fine motor coordination and behavior regulation in children ages 7 to 10 years old. (Thimerosal, a mercury-containing preservative, was removed from children's vaccines a decade ago due to worries about its relationship to the onset of autism; it is still used in some influenza vaccines made in bulk.)

Dr. Smith's study looked at subsets of test results for 1,047 children vaccinated from 1993 to 1997, comparing results for a group vaccinated on time—that is, they received 10 shots by the age of seven months—with a group whose vaccinations were delayed.

The analysis found little difference in results for children in both on-time and delayed vaccination groups. The on-time group did slightly better on an intelligence test and a little faster on a test asking children to name things. "There's not a single variable where the delayed kids did better," Dr. Smith said.

But delays have a major downside: They put children at risk for developing diseases the vaccines are designed to ward off. In 2008, five cases of illnesses caused by the bacterium Haemophilus influenzaeType B, including one death, were reported in Minnesota during a 2008 shortage of the Hib vaccine, which babies get at the ages of 2, 4 and 6 months with a booster shot between 12 and 15 months. In three of the cases, the babies hadn't received the Hib vaccine, and the other two babies hadn't been fully vaccinated. The Hib bacterium can cause pneumonia and meningitis.

Concerns about vaccine safety have lingered, prompted partly by a now-withdrawn study linking the MMR vaccine (for measles, mumps and rubella) with the onset of autism. More than 90% of babies are vaccinated, but only 76% of children from the ages of 19 to 35 months get all recommended doses of key vaccines, according to data released last year by the Centers for Disease Control and Prevention. Fewer than 1% of children receive no vaccines.

Dr. Smith likens a parent's decision to delay vaccination to someone buckling their seat belt after 20 minutes of riding in the car. "You don't know when you'll get hit," he says.

Paul Offit, a vaccine expert and chief of the division of infectious diseases at the Children's Hospital of Philadelphia, who wasn't involved in the study, says, "When you watch your kids get five shots, it's perfectly reasonable to ask if it's too much." Dr. Offit helped develop Merck & Co.'s Rotateq rotavirus vaccine and served on the U.S. panel overseeing children and adult vaccination schedules.

Recommended vaccines are designed to prevent infection with 14 diseases. Babies can receive up to 26 vaccines in their first year of life, Dr. Offit said—a doubling since the mid-1980s.

Infants typically get a Hepatitis-B vaccine at birth and five or six vaccinations at each of their 2-, 4- and 6-month visits to protect against illness like polio, rotavirus, diphtheria, tetanus, pertussis and pneumococcal disease (which can cause meningitis and pneumonia). At 12 to 15 months, vaccines against measles, mumps and rubella, Hepatitis A and varicella (the virus that causes chicken pox) are recommended. All are administered in a series of two-to-four doses and, except for the oral rotavirus vaccine, all are injected. In addition, children older than 6 months are advised to get an annual flu vaccine.

Dr. Offit says the viral material in vaccines for babies is "literally a drop in the ocean" compared with how much bacteria a baby's immune system copes with each day. One bacterium typically will have from 2,000 to 6,000 antigens, while the five or six vaccines given to a baby in one doctor's visit have about 150 antigens in all.


Resource

WALL STREET JOURNAL, No Benefit in Delayed Immunization, Jennifer Corbett Dooren, http://online.wsj.com/article/SB10001424052748704113504575264421687548864.html?mod=WSJ_hp_editorsPicks, 05/24/10.