Abstract
Objective: To assess the immunity status against vaccine-preventable diseases in the Expanded Program on Immunization (EPI) program, including hepatitis B, measles, mumps, rubella, diphtheria, tetanus and pertussis, along with other important diseases or vaccine-preventable diseases in the EPI pipeline (hepatitis A, hepatitis C and varicella) in Thai individuals residing in Chonburi Province, Thailand. Methods: A cross-sectional descriptive study was conducted in Chonburi Province between October 2022 and February 2023. The subjects in this study consisted of the population living in Chonburi province from birth to 80 years of age. Participants were grouped into age categories based on ten-year intervals. The level of immunity against hepatitis A, B, C, measles, rubella, mumps, varicella, diphtheria, tetanus, and pertussis. Results: A total of 1,459 subjects met the selection criteria and were enrolled. Seroprevalence rate against hepatitis A (anti-HAV IgG) were low in individuals below 40 years of age. The overall trend showed an increase in seroprevalence with age. For immunity against hepatitis B, children and young adults who were born after implementation of infant universal Hep B vaccination in Chonburi Province in 1988 had seroprevalence of HBsAg less than 1%, anti-HBc less than 3%. The anti-HBs levels were highest in children under 5 years of age. These findings are consistent with the integration of Hep B vaccination into the EPI. For anti-HCV, seroprevalence rate was 1%, with the majority of seropositive individuals being adults and elderly. Seroprevalence against measles, mumps and rubella in 657 individuals across all age groups showed that individuals between 11-20 years old possessed the lowest immunity. Older adults and elderly possessed high levels of immunity against measles and mumps, whereas children under 5 years of age and the elderly possessed high levels of immunity against rubella. Results of anti-diphtheria toxoid IgG (anti-DT IgG) in 657 individuals across all age groups showed that 65.4% of individuals were seroprotective as defined by anti-DT IgG ≥0.1 IU/mL. The lowest seroprotection rate for anti-DT IgG was found in 31–40-year-old age group (48.9%), followed by 51-60-year-old age group (50.5%) and 41-50-year-old age group (56.9%). Regarding the anti-tetanus toxoid IgG (anti-TT IgG), 95.1% of individuals were seroprotective with the lowest seroprotection rate found in 60-70-year-old and ≥ 70 year-old age groups. In contrast, the geometric mean titers against pertussis toxin were highest in children under 5 years due to recent vaccination. The results of anti-varicella IgG shows that the seroprevalence increases with age, starting at 20 years old. Conclusion: The immunity status against hepatitis A, B, C, measles, rubella, mumps, chickenpox virus, diphtheria, tetanus and pertussis showed that the seroprotection rates are under achieved in the following diseases: diphtheria, pertussis, measles, mumps, rubella, in different age groups as described. After the COVID-19 pandemic has subsided, revisions of the vaccine policy should be performed in order to prevent the outbreak of vaccine-preventable and other relevant diseases. The study's findings are preliminary for one province, but they provide valuable data on the immunity status against vaccine-preventable diseases. This will help guide the vaccine policy development for Thailand in the future.
