Effect of smoking on long-term immunity after hepatitis B vaccine in infancy. A 20-year cohort study

The immune response to hepatitis B vaccination has been shown to be associated with a number of different factors, including age, sex, BMI, comorbidities and modifiable determinants, including smoking. However, while there is a strong evidence suggesting that smokers are at higher risk of not responding to the vaccine, the effect of smoking on long-term antibody persistence is not fully understood. Therefore, we aimed to evaluate the effect of smoking habit on long-term immunity (∼20 years) after primary vaccination. Individuals were recruited on the occasion of the occupational health surveillance medical examination at the University of Padova, Italy. Participants had to have received a standard 3-dose schedule in infancy (2-12 months of age) with no subsequent booster dose, and be 18-24 years of age at the enrolment. Information was collected on age, sex, body mass index (BMI), age at first dose and interval between doses. Antibody titres <10IU/l were considered non-protective according to international standards. Given the young age of the participants, current and former smokers were considered together. A single-step logistic regression was performed to assess the effect of smoking on a non-protective antibody titre, adjusting for all variables considered. A total of 2,133 individuals were included, of whom 62.6% were female. The mean age of the participants was 20.28±0.92 years. The risk of a non-protective antibody titre was significantly higher in smokers compared to non-smokers (AOR: 1,287; 95%CI: 1,002-1,652). Smokers have a + 29% risk of having antibody levels below the recommended threshold when assessing long-term immunity, although it should be noted that a titre <10IU/l does not automatically mean lack of protection. Smoking habit not only negatively affects the short-term response to the vaccine in adults, but also the long-term immunity when vaccinated in infancy, making the need for additional immunity enhancement in this subpopulation reasonable. KEY MESSAGES: • Smoking has a negative effect on long-term immunity (about 20 years) after hepatitis B vaccination in infancy, not just on short-term responsiveness in adults. • Smokers have a + 29% higher risk of having a non-protective antibody titre, raising the question of the need for additional immunity enhancement in this subpopulation.