A new study questions whether adults require tetanus or diphtheria booster shots if they have already completed their childhood vaccination series against the rare, yet debilitating, diseases.

The research published in Clinical Infectious Diseases is in line with the World Health Organization's recent recommendations to routinely give adults tetanus and diphtheria vaccines only if they did not receive a full series of shots as children. In the United States, however, the CDC’s Advisory Committee on Immunization Practices still recommends that all adults receive booster shots every 10 years.

Oregon Health & Science University School of Medicine–led researchers were unable to identify any significant difference in disease rates between countries that require adults to receive tetanus and diphtheria booster shots and those that do not. To reach their conclusion, they compared data from millions of people from 31 North American and European countries between 2001 and 2016. Countries that vaccinate adults every 5 to 20 years (group 1) were compared with countries that do not routinely vaccinate adults for tetanus or diphtheria (group 2). 

The observational cohort study found no significant decline in tetanus incidence rates among countries that vaccinate adults (P = .52; risk ratio [RR] = 0.78; 95% confidence interval [CI], .36-1.70). 

Researchers note that the risk of contracting diphtheria was increased among countries that vaccinate adults due to the inclusion of Latvia, a country that had poor vaccination coverage (P < .001). When the nation was excluded, however, there was no difference in diphtheria incidence between countries that do or do not routinely vaccinate adults (P = .26; RR = 2.46; 95% CI, .54-11.23).

“Review of >11 billion person-years of incidence data revealed no benefit associated with performing adult booster vaccinations against tetanus or diphtheria,” lead author Mark Slifka, PhD, and colleagues conclude. “Similar to other vaccines, this analysis supports the WHO position on adult booster vaccination and, if approved by governing health authorities, this may allow more countries to focus healthcare resources on vulnerable and under-vaccinated populations.”

The report suggests that requiring fewer vaccinations for adults could save the United States about $1 billion annually in unnecessary medical costs.
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Earlier research by Dr. Slifka and colleagues, published in 2016, concluded that the vaccine produced at least 30 years of immunity for the 546 adults in that study. As a result, the researchers recommended at that time to vaccinate adults against these diseases only every 30 years.

“Based on our new data, it turns out we were probably overly conservative back in 2016,” Dr. Slifka says. “Even though it looked like immunity could be maintained for decades, we didn’t have direct evidence back then that this would translate into true protection against disease in the real world.

“However, our new data provides the final piece to the puzzle. We now have evidence showing the childhood vaccination series can provide a lifetime of protection against both tetanus and diphtheria.”

Adds Dr. Slifka, “To be clear, this study is pro-vaccine. Everyone should get their series of tetanus and diphtheria shots when they’re children. But once they have done that, our data indicates they should be protected for life.”

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