Despite WHO recommendation to discontinue booster vaccination for diphtheria and tetanus once childhood vaccinations are completed, many countries still follow this practice. However, research now shows that this is completely unnecessary. Published in the journal Oxford Academic, the study found no benefit of administrating adult booster vaccinations against tetanus and diphtheria if the childhood vaccination series is completed. The researchers hoped that these results would allow the health authorities in concerned countries to focus on other vulnerable areas. 
The research team from the Oregon National Primate Center used WHO case reports from 2001-16 for their study. They conducted an observational cohort study of the data. 21 countries in Europe and North America were studied. This included countries that recommended as well as did not recommend adult booster doses. These countries were split in two groups with group one consisting of countries with adult booster doses and group 2 of no adult booster doses.
A comparison of the two groups revealed that the drop in tetanus incidence rates was insignificant in countries with adult vaccination. Interestingly, they found that cases of diphtheria increased were higher in countries with adult vaccination. But they concluded that this could be due to the inclusion of Latvia where vaccination coverage is still poor. Once Latvia was removed from the equation, there was almost no difference in cases.