Tetanus diphtheria booster shots not needed by adults says study

By Dr. Ananya Mandal, MDFeb 25 2020

According to the latest research, if adults have been entirely vaccinated as children, they need not get booster shots for diphtheria and tetanus. The study is published today in the latest issue of the journal Clinical Infectious Diseases and is titled, "Incidence of Tetanus and Diphtheria in Relation to Adult Vaccination Schedules."

Adults do not need tetanus or diphtheria booster shots if they've already completed their childhood vaccination series. Image Credit: PanyaStudio / Shutterstock

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Tetanus and diphtheria are deadly bacterial infections that were a significant killer a few decades back. Now with complete vaccination, these infections can be largely avoided.

Tetanus or lockjaw leads to severe muscle spasms and can be spread via feces and dirt or contaminated nails or needles. The infection is detected in around 30 individuals every year, and of these, 1 in 10 may succumb to the infection.

The deaths and infections are seen only among those who have not been vaccinated or have incomplete vaccination, explained experts.

Diphtheria is another severe bacterial infection that causes the formation of a thick layer at the back of the throat and can lead to difficulty in breathing and even death in children.

Less than five cases of diphtheria are seen annually in the US, and of these, one in 10 cases is fatal. Infection and fatalities are more prevalent among the unvaccinated. Before the routine vaccination, diphtheria killed 1,800, and tetanus killed 470 individuals every year, respectively, in the United States.

The World Health Organization (WHO) has also recently said that adults need to be routinely vaccinated against tetanus and diphtheria if they have not received a complete vaccination course as children.

At present, the United States Centre for Disease Prevention and Control (CDC) recommendations, however, advise in their Advisory Committee on Immunization Practices that all adults need such booster shots every ten years.

The team of researchers looked at immunization data from over 11 billion individuals from 31 different nations in North America and Europe between 2001 and 2016 to see if there was any advantage provided by the booster shots. This was an observational cohort study that looked at the new cases of tetanus and diphtheria in these nations.

Results

The team of researchers divided the populations from the countries into two groups – group 1 included countries that vaccinated adults every 5 to 20 years, and group 2 included countries that did not vaccinate adults routinely against tetanus and diphtheria.

Results showed that there was no decline in the number of cases of tetanus and diphtheria in group 1 compared to group 2. A relative risk of 0.78 was found.

The team added that Latvia was one of the nations that had inadequate vaccination coverage for adults, and this raised their risk of getting diphtheria. If they excluded Latvia from the analysis, the incidence of tetanus and diphtheria among vaccinated and non-vaccinated countries was similar with no difference, they wrote.

Implications

Mark Slifka, the lead author of the study, professor at the Oregon Health & Science University School of Medicine and the Oregon National Primate Research Center, said, "To be clear, this study is pro-vaccine. Everyone should get their series of tetanus and diphtheria shots when they're children. However, once they have done that, our data indicates they should be protected for life." He explained that their previous study from 2016 also showed that once vaccinated against these infections as children, the immunity provided lasts for around three decades.

He said, "Based on our new data, it turns out we were probably overly conservative back in 2016. Even though it looked like immunity could be maintained for decades, we did not 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," he added.

Slifka said that if the study findings are followed, the US will save around $1 billion annually in healthcare costs needed to vaccinate adults with these booster shots. The team wrote in 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 under-vaccinated populations."

This study was supported by the National Institutes of Health and the Oregon National Primate Research Center.