INTRODUCTION: mumps vaccination implementation in the form of MMR - measles, mumps, and rubella) in Thailand for first-grade school students since 1997 and for infants 9-12 months of age since 2010 resulted in a dramatic decline in the incidence of and deaths from mumps. However, there has been a resurgence of mumps outbreaks in Thailand, even in vaccinated populations. METHODOLOGY: We aimed to determine the current seroprevalence of IgG antibodies to mumps in those 0-60 years of age from four different geographic areas of Thailand, and compare the results with our previous serosurvey in 2004. RESULTS: Seropositivity rates in children 0-7 years of age increased significantly from 45.8% in 2004 to 72.3% in 2014 after the launch of the MMR vaccine for infants. In the 8-14-year age group who had received one dose of mumps vaccination, the seropositivity rate was 66.7%. In the 15-19-year age group the seropositivity rate was the lowest, at 52.5%. DISCUSSION: Our findings correspond well with the vaccination schedules, as the highest seropositivity rate was found in children between 0 and 7 years of age. For those older than 7, there was a decline in seropositivity rate despite good vaccine coverage and reached its lowest in the 15-19-year age group. This suggested that certain population groups might be incompletely vaccinated, or the humoral immunity provided by vaccination gradually declined over time. CONCLUSIONS: We recommend a booster dose of MMR vaccine for Thai adolescents in order to prevent future mumps outbreaks.
INTRODUCTION: mumps vaccination implementation in the form of MMR - measles, mumps, and rubella) in Thailand for first-grade school students since 1997 and for infants 9-12 months of age since 2010 resulted in a dramatic decline in the incidence of and deaths from mumps. However, there has been a resurgence of mumps outbreaks in Thailand, even in vaccinated populations. METHODOLOGY: We aimed to determine the current seroprevalence of IgG antibodies to mumps in those 0-60 years of age from four different geographic areas of Thailand, and compare the results with our previous serosurvey in 2004. RESULTS: Seropositivity rates in children 0-7 years of age increased significantly from 45.8% in 2004 to 72.3% in 2014 after the launch of the MMR vaccine for infants. In the 8-14-year age group who had received one dose of mumps vaccination, the seropositivity rate was 66.7%. In the 15-19-year age group the seropositivity rate was the lowest, at 52.5%. DISCUSSION: Our findings correspond well with the vaccination schedules, as the highest seropositivity rate was found in children between 0 and 7 years of age. For those older than 7, there was a decline in seropositivity rate despite good vaccine coverage and reached its lowest in the 15-19-year age group. This suggested that certain population groups might be incompletely vaccinated, or the humoral immunity provided by vaccination gradually declined over time. CONCLUSIONS: We recommend a booster dose of MMR vaccine for Thai adolescents in order to prevent future mumps outbreaks.