Booster shots for tetanus and diphtheria not necessary if vaccinated in childhood

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Adults don’t need tetanus and diphtheria boosters if they were fully vaccinated as children, a study has found. The conclusion aligns with the World Health Organisation‘s recent recommendations to only routinely give adults tetanus and diphtheria vaccines if they didn’t receive a full series of shots as children. In the US, the Centres for Disease Control and Prevention‘s (CDC‘s) Advisory Committee on Immunisation Practices still recommends all adults receive booster shots every 10 years.

Dr Mark Slifka and colleagues found no significant difference in disease rates between countries that require adults to receive tetanus and diphtheria booster shots and those that don’t. The finding is the result of comparing data from millions of people from 31 North American and European countries between 2001 and 2016.

“To be clear, this study is pro-vaccine,” says Slifka, the study’s lead researcher and a professor at the Oregon Health & Science University School of Medicine and the Oregon National Primate Research Centre. “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.”

Requiring fewer vaccinations for adults could save the US about $1bn annually in unnecessary medical costs, the researchers estimate.

The paper follows research Slifka and colleagues published in 2016, which concluded 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,” Slifka now 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.”

Tetanus, also known as lockjaw, is a bacterial infection that causes jaw cramping, painful muscle spasms, trouble swallowing and breathing, seizures, convulsions and, in severe cases, death. It’s spread by bacteria commonly found in dirt or faeces, or on contaminated objects such as nails or needles. About 30 people in the USget tetanus annually, and one or two out of 10 cases can be fatal. Tetanus-associated deaths almost always occur among unvaccinated people, or those with incomplete or unknown vaccination history.

Diphtheria is a bacterial infection that causes a thick covering in the back of the throat, which can lead to difficulty breathing, heart failure, paralysis or death. It’s spread by exposure to infected people or in rare cases, infected animals. In the past decade, less than five US cases of diphtheria were reported to the CDC. In an unvaccinated population, about one in 10 cases can be fatal. But more than 99.8 percent of vaccinated people who are diagnosed with diphtheria and receive appropriate care survive.
In the pre-vaccine era, there were about 470 tetanus-associated deaths and 1,800 diphtheria-associated deaths in the US each year. Tetanus- and diphtheria-related deaths have declined by more than 99% since vaccines became available to prevent them.

Background: The World Health Organization (WHO) does not recommend routine adult booster vaccination for tetanus and diphtheria after completion of the childhood vaccination series. However, many countries continue to implement adult booster vaccinations, leading to the question of whether this is necessary to reduce the incidence of these 2 rare diseases.
Methods: We conducted an observational cohort study based on WHO case reports from 2001 through 2016. We compared the incidence of tetanus and diphtheria in 31 North American and European countries that either do or do not recommend adult booster vaccination.

Results: Countries that vaccinate adults every 5–20 years (group 1) were compared with countries that do not routinely vaccinate adults for tetanus or diphtheria (group 2). Comparison of group 1 vs group 2 revealed no significant decline in tetanus incidence rates among countries that vaccinate adults (P = .52; risk ratio [RR] = 0.78; 95% confidence interval [CI], .36 to 1.70). The risk of contracting diphtheria was increased among countries that vaccinate adults due to inclusion of Latvia, a country that had poor vaccination coverage (P < .001). However, if Latvia is excluded, there is no difference in diphtheria incidence between countries that do or do not routinely vaccinate adults (P = .26; RR = 2.46; 95% CI, .54 to 11.23). Conclusions: Review of >11 billion person-years of incidence data revealed no benefit associated with performing adult booster vaccinations against tetanus or diphtheria. 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 undervaccinated populations.

Mark K Slifka, Lina Gao, Byung Park, Ariel M Slifka

Oregan Health & Science University material

Clinical Infectious Diseases abstract

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