September 18, 2019
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Broad-spectrum antibiotics may weaken flu vaccine response

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Bali Pulendran, PhD
Bali Pulendran

Healthy adults who take broad-spectrum antibiotics may impair their body’s immune response to influenza vaccination, according to findings from a small study published in Cell.

“Strikingly, this effect on the antibody response was only evident in people who had not received the influenza shot or been infected with influenza for the past 3 years, suggesting that robust immune memory imprinted by prior exposure to the vaccine or influenza could withstand even the most severe dysbiosis in the gut microbiota,” Bali Pulendran, PhD, from the department of pathology and laboratory medicine at Emory University School of Medicine, told Infectious Disease News.

According to Pulendran and colleagues, evidence has indicated a central role for the microbiome in immunity, but causal evidence in humans is sparse. To determine whether antibiotic-driven depletion of the gut flora can impact responses to vaccination, the researchers administered trivalent influenza vaccine to 22 healthy adults aged 18 to 45 during the 2014-2015 influenza season and randomly assigned 11 participants to a 5-day course of oral broad-spectrum antibiotics, beginning three days before vaccination.

They used stool and blood serum samples to profile participants’ immune responses to vaccination and the diversity and abundance of the organisms in their gut microbiome, according to an NIH news release.

They found that profound antibiotic-driven perturbation of participants’ gut microbiome — a 10,000-fold reduction in gut bacterial load and long-lasting diminution in bacterial diversity — resulted in a significant impact on the H1N1-specific immunoglobulin G1 response in subjects with low pre-existing antibody titers. Antibiotic treatment also had a “striking effect” on the plasma metabolome, with a 1,000-fold reduction in serum secondary bile acids, according to Pulendran and colleagues. This was highly correlated with elevated cellular and transcriptional signatures of inflammation, they said.

“This was a relatively small study in a controlled experimental medicine setting, so it is important to confirm these results in larger studies,” Pulendran said. “In particular, research should focus on diverse populations in natural settings, such as infants during the first year of life receiving antibiotics and the ensuing effect of this on their response to childhood vaccination.”

Pulendran noted that this is yet another indication that extensive unnecessary antibiotic use has the potential to do “real harm.” – by Joe Gramigna

Disclosures: The authors report no relevant financial disclosures.