Antibiotics Tied to Lower Effectiveness of Childhood Vaccines

Use of the drugs in children under the age of two was associated with lower antibody levels after the jabs—perhaps, researchers suggest, due to microbiome alterations. The drugs disrupt gut bacteria, which appear to play a part in the body’s response to vaccines

Babies are typically immunized against various diseases in the first six months of life and get boosters in their second year. From 2000 to 2016, the study’s authors collected blood samples from 560 children ages 6 to 24 months during routine visits with their pediatricians, measuring antibody levels after the children received polio, diphtheria-tetanus-pertussis, Haemophilus influenzae type b, and pneumococcal vaccines. 

Of these children, 342 had collectively been prescribed close to 1,700 courses of antibiotics. The other 218 children had not received antibiotics. The team analyzed whether antibody levels induced by the four vaccines met the threshold of what is considered protective and found that at 9 and 12 months old, children who had received a course of antibiotics were significantly more likely to have subpar levels of antibodies than those who had not. The immune response was lower among children who’d had multiple courses of antibiotics than for those who’d had one, with each antibiotics dose associated with 5 to 11 percent lower antibody levels after initial vaccinations and 12 to 21 percent lower antibodies after booster shots. 

Taking antibiotics in the first two years of life can prevent babies from developing a robust immune response to certain vaccines. The new finding provides another cautionary tale against overusing antibiotics, researchers say.

Babies get immunized in their first six months, and receive booster doses in their second year, to protect against certain infectious diseases. Antibiotic use during that time was associated with subpar immune responses to four vaccines babies receive to ward off whooping cough, polio and other diseases, researchers report online April 27 in Pediatrics.

And the more rounds of antibiotics a child received, the more antibody levels to the vaccines dropped below what’s considered protective. Levels induced by the primary series of shots for the polio, diphtheria-tetanus-pertussis, Haemophilus influenzae type b and pneumococcal vaccines fell 5 to 11 percent with each antibiotic course. In the children’s second year, antibody levels generated by booster shots of these vaccines dropped 12 to 21 percent per course.

If anyone needed yet another reason why overprescription of antibiotics is not a good thing, this research results offers that reason.

Taking antibiotics disrupts the population of bacteria that live in the gut. That’s well known, but researchers are still learning about how that disruption can affect a person’s health. The new study adds to evidence that diminishing the amount and diversity of gut bacteria impacts vaccination. In studies in mice, antibiotics hampered the immune system’s response to vaccines. And a small study in humans found that antibiotics dampened adults’ response to the flu vaccine in those whose prior immune memory for influenza had waned. (1)

The study in Pediatrics is the first to report an association between antibiotic use and compromised vaccine responses in children. 

The type and length 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. Furthermore, a 10-day course, but not a five-day course, reduced vaccine-induced antibody levels.

T.J. Chapman et al. Antibiotic use and vaccine antibody levels. Pediatrics. Published online April 27, 2022. doi: 10.1542/peds.2021-052061

T. Hagan et al. Antibiotics-driven gut microbiome perturbation alters immunity to v.... Cell. Vol. 178, September 2019, p. 1313. doi: 10.1016/j.cell.2019.08.010