Taking antibiotics during the first two years of life can prevent babies from developing a robust immune response to some vaccines. The new finding provides another warning against the overuse of antibiotics, the researchers say.
Babies are vaccinated during their first six months and receive booster doses during their second year, to protect against certain infectious diseases. Antibiotic use during this period was associated with lower immune responses to four vaccines babies receive to ward off whooping cough, polio and other illnesses, researchers report online April 27 in Pediatrics.
And the more antibiotics a child received, the further the vaccine antibody levels fell below what was considered protective. Levels induced by the first series of injections for poliomyelitis, diphtheria-tetanus-pertussis, Haemophilus influenzae type b and pneumococcal vaccines dropped 5-11% with each antibiotic treatment. During the children’s second year, antibody levels generated by booster shots of these vaccines dropped by 12-21% per cycle.
“If anyone still needed another reason why overprescribing antibiotics is not a good thing, this article offers that reason,” says immunologist Bali Pulendran of Stanford University School of Medicine, who did not participate in the study.
Taking antibiotics disrupts the population of bacteria that live in the gut. It’s well known, but researchers are still learning how this disruption can affect a person’s health. The new study adds to the evidence that decreasing the amount and diversity of gut bacteria impacts vaccination. In mouse studies, antibiotics interfered with the immune system’s response to vaccines. And a small study in humans found that antibiotics dampened adult response to flu vaccine in those with diminished prior immune memory for influenza, Pulendran and colleagues reported in 2019.
The study in Pediatrics is the first to report an association between antibiotic use and compromised vaccine responses in children. Michael Pichichero, a pediatric infectious disease specialist at the Rochester General Hospital Research Institute in New York, and his colleagues took blood samples taken from 560 children during routine visits with their pediatricians. Of these, 342 children had been prescribed nearly 1,700 courses of antibiotics and 218 children had not received the drugs. The team analyzed whether the levels of antibodies induced by the four vaccines reached the threshold considered protective and found levels more often insufficient for children who had received antibiotics.
The type and duration of antibiotic treatment also made a difference. Broad-spectrum drugs were associated with antibody levels below what is protective, while a more targeted antibiotic was not. Additionally, a 10-day course, but not a five-day course, reduced vaccine-induced antibody levels.
The researchers did not investigate whether children in the study with decreased antibody levels were more likely to develop vaccine-preventable diseases. But there have been concerns about whooping cough outbreaks, Pichichero says, that have occurred in the United States despite vaccination (SN: 04/04/14). Perhaps the use of antibiotics can help explain these outbreaks, he says.
To see what kinds of changes occur in gut bacteria, Pichichero and his colleagues are starting a study with a new group of children. Researchers will collect stool samples along with blood draws and antibiotic usage records. They would like to follow children after age 5, beyond when children receive another round of boosters, to find out if antibiotics also interfere with this next opportunity to develop antibodies.
“Antibiotics are miracle drugs,” says Pichichero. “This study in no way implies that children who need an antibiotic should not take it.” But if possible, it should be a narrowly targeted antibiotic for shorter treatment, he says. In addition to the risk of antibiotic resistance that accompanies drug overuse (SN: 01/24/22), the impact that antibiotics might have on vaccine-induced immunity “has clinical implications for every child.”