Do antibiotics reduce vaccine effectiveness in infants?

A landmark Australian study published in the respected journal Nature has shown a link between giving antibiotics to newborns and a dampened immune response to routine immunisations.

“This has raised parental concerns, as immunisations provide important protection from serious, potentially fatal conditions,” says Durban-based specialist paediatrician Dr Ridwan Omar. DTaP, for example, protects against diphtheria, tetanus and pertussis (whooping cough); PCV (pneumococcal conjugate vaccine), against meningitis, bloodstream infections and pneumonia; Hib (Haemophilus influenzae type b), against severe bacterial infections; and IPV (inactivated poliovirus vaccine), against polio.

The study tracked healthy babies from birth to 15 months, monitoring how their immune systems responded to vaccines. They found that by seven and 15 months of age, those given antibiotics in the first weeks after birth had lower levels of antibodies against many different vaccine antigens (the active ingredients in a vaccine that generate an immune response against disease-causing organisms), compared to babies not given antibiotics.

This is attributed to antibiotics disrupting the infants’ beneficial gut bacteria, especially Bifidobacteria, which play a vital role in an optimal immune system. “Broad-spectrum antibiotics inadvertently kill off these beneficial bacteria,” says Dr Omar.

Why more research is needed

There are still many unknowns about the interaction between the gut microbiome and vaccination responses, he says. While the reduction in antibodies due to antibiotics means a higher percentage of infants drop below optimal protective thresholds, some infectious disease researchers have said that a lower concentration of specific antibodies in the blood does not always translate to reduced protection.

There may soon be a solution at hand. The same Australian researchers who did the Nature study are now conducting a clinical trial to test if giving infants who have been treated with antibiotics a probiotic that contains Bifidobacterium before the infants’ first immunisations can improve their antibody responses to vaccinations. They anticipate that probiotics may have a significant impact on infant health going forward, providing a relatively cheap way to boost vaccine protection.

Vaccine and antibiotic best practice for parents

Despite the publication of the Nature study, global health agencies such as the World Health Organization stand by clear guidelines regarding immunisation and antibiotics.

Do not postpone vaccinations

Children currently taking antibiotics for mild illnesses such as ear infections should still receive their vaccines, as delays leave them unprotected against severe diseases, says Dr Omar. However, if your child has a moderate to severe illness with a high fever, you may need to wait until they are better to administer some vaccines. “Ask your healthcare provider or a clinic nurse,” he says. Your child may not receive some vaccines if they have a chronic health condition (such as cancer) or are on chemotherapy, or had a severe allergic reaction to a previous dose of a vaccine or an ingredient in it. 

Use antibiotics responsibly

Never ask for them for viral infections such as colds, flu or RSV (respiratory syncytial virus), he says. Antibiotics target bacteria, not viruses, so cannot help. Misusing or overusing antibiotics allows bacteria to build resistance to them, as the strongest survive and multiply. Antibiotic-resistant infections are harder to treat, last longer and lead to more serious illnesses that may require hospitalisation.

Ask for an alternative

If your healthcare provider prescribes antibiotics for your child, ask if there is an alternative, such as waiting 48–72 hours to see if symptoms resolve before starting antibiotics. If antibiotics are prescribed, give them exactly as directed and always finish the course (not finishing the entire course increases the risk of antibiotic-resistant strains of bacteria developing). 

Do not worry unduly if your newborn is treated with antibiotics

The lead researcher in the Nature study has himself told media that “there’s usually very good reason for giving the neonates those antibiotics, given that infections and sepsis in that critical early life period can be very serious”.