Vaccine combination leads to fevers, more ER visits for babies
Infants receiving a new combination of vaccines were twice as likely to require medical attention for fevers after their shots as babies who received the prior shot regimen, University of Florida and Columbia University researchers have found.
Babies who received a new shot that mixes five vaccines into one at the same time they were given two other standard shots visited the emergency room, underwent blood tests and were treated with antibiotics more often than other babies, the researchers write in the current issue of The Pediatric Infectious Disease Journal.
"Reducing the number of shots is wonderful, but it just happens that when you combine it with two other shots also routinely given, there is an increased risk of fever," said Lindsay A. Thompson, M.D., M.S., a UF assistant professor of pediatrics and the study's lead author. "This study shows that beyond the important safety and efficacy studies the FDA requires there are often unintended consequences when you apply any new technology to the real-life Petri dish."
The new vaccine, introduced in 2003, protects against diphtheria, tetanus, pertussis, polio and hepatitis B. It allows doctors to give infants one shot instead of several different shots. The other two shots, which combine with the new vaccine to cause more fevers, protect against bacterial infections such as pneumonia and meningitis.
Before pediatricians widely adopt new vaccines, they should decide how to address issues like these to best treat their tiniest patients, the researchers suggest in the study. This is particularly important as new vaccines continue to be introduced, Thompson said.
While these fevers are generally harmless to infants, they create a two-pronged problem for pediatricians, Thompson said. Doctors treat fevers aggressively in infants 3 months old or younger, which is when most babies receive their first shots. Dangerous bacterial infections are to blame for about 10 percent of infant fevers, which doctors would not want to miss, she said. Because of this, infants with vaccination-related fevers might go through unnecessary testing, such as a spinal tap, or be exposed to emergency room germs. There's also the chance that some doctors will begin to overlook a fever after a baby has been vaccinated, passing it off as a side effect of a vaccine when it could actually be something more serious.
Of the nearly 4,000 records researchers combed from Columbia University's health-care system, where Thompson completed the research, 1 out of every 100 babies visited the emergency room for fevers after their shots. Researchers did not measure the number of parents who may have just called their doctors or decided to treat the fever at home, she said.
"In the scheme of things, 1 out of 100 babies going to the emergency room is not a massive burden across the U.S., but I think for each family it is," Thompson said.
The researchers found that after using the vaccine for awhile, many doctors seemed to delay when they gave the shot to babies, likely because infants generally are not treated as aggressively for fevers after they are 2 months old, Thompson said.
"That, I think, is problematic because there is a real need to vaccinate all children as soon as possible," she said. "Some families may have a hard time getting back to the clinic. You could miss giving a child an immunization."
Waiting to vaccinate until a child is 8 weeks old also may be putting the infant at risk, said Tobias R. Kollmann, M.D., Ph.D., an assistant professor of pediatric infectious and immunological diseases at the University of British Columbia. Some conditions doctors vaccinate against, such as pertussis, make adults sick but can kill a 6-week-old infant, he said.
Kollmann said the UF study highlights the biggest need for pediatricians, health workers and parents: more education and communication about vaccines. The more doctors and nurses know about vaccines, the more parents will know, improving the chances that all children will be vaccinated, he said.
"It's an important finding," he said. "The biggest hurdle is education. Everyone involved needs to be up-to-speed."
Thompson stresses that the combination vaccine is safe and used across the United States and in UF clinics. But she emphasizes the need for more research into how to best evaluate children with fevers after vaccines to avoid exposing them to unneeded tests and antibiotics.
"One of my primary interests as a pediatrician is to make sure every child is vaccinated," she said. "But I think we work in an isolated way. Researchers work on vaccines. Primary care physicians work on primary care. I think there needs to be more overlap between new technologies and the real world."