Backgrounds:

The presence of maternal transplacental measles antibodies in infants can prevent infection in early life but also suppress the infant response to the first measles vaccine.

Methods

We explored factors associated with antibody levels in mothers and infants at birth, and the decay of antibody in the first year of life in a multicountry seroprevalence study to determine the decay of maternal antibodies and loss of protection, and whether these vary geographically. Stored sera from mothers and infants were shipped to a central laboratory for evaluation of anti-measles IgG by multiplex immunoassay and plaque reduction neutralisation titres (PRNT). Data from the first five countries were available for analysis (Mali, Thailand, The Netherlands, UK, Vietnam)

Log-transformed data were compared using linear models adjusting for country. Decay models included polynomial terms and infant level random intercepts to account for the repeated timepoints.

Results:

Higher measles serum IgG and PRNT were statistically associated with maternal age, in both maternal samples (IgG p=0.001, PRN p=0.003) and cord blood (IgG p=0.037, PRN p=0.015). Maternal age was also statistically significantly related to the WHO measles vaccine coverage during the mother’s year of birth, indicating that older mothers are less likely to have been vaccinated in early life than younger mothers resulting in higher antibody in later life from childhood infection.

Measles IgG and PRNT in infant samples decayed at a similar rate across all countries in the first 6 months of life. Average PRNT were below protective thresholds (120 mIU/ml) by 6 months of age for all countries. For anti-measles IgG, all countries had seronegative estimates at 9 months of age.

Conclusions/Learning Points:

Infants older than 6 months are susceptible to measles infection. These results can inform vaccination programmes.

Backgrounds:

Only 10 of the 27 EU countries offer gender-neutral HPV-vaccination. In most of them, uptake is lower in boys than in girls. From the school year 2019-2020 onwards, the Flemish government offers gender-neutral free HPV-vaccination in the first year of secondary education, thereby including adolescent boys in its vaccination strategy. In 2021, a survey was performed using the WHO’s EPI-method to assess (among others) adolescent HPV-vaccination coverage in Flanders, Belgium.

Methods

A total of 955 adolescents (°2007) were recruited in 103 municipalities through a two-stage randomized cluster design. After signing informed consent, a parent/caregiver of the adolescent was interviewed at home or through video call (pandemic-dependent). Available documents on vaccination history of the child were transcribed and later completed with information from the electronic Flemish vaccination registry and medical records. The coverage of recommended vaccines in childhood and adolescence was assessed, including HPV-vaccination in boys and girls.

Results:

Overall, 854 adolescents received a first dose of the HPV vaccine (89.4%), and 771 received a second dose (80.7%). In girls, who have been offered HPV-vaccination since 2010, the coverage reached 92.3% and 84.3% for the first and second dose, respectively. Notably, 88.1% of boys in our cohort, who were the first to be offered HPV-vaccination, had received a first (p=0.05 vs. girls), and 78.4% a second dose (p<0.001 vs. girls).

Conclusions/Learning Points:

The first year after the implementation of HPV-vaccination in boys already spurred an immense uptake. The coverage for the first dose is only marginally below that of girls but comparable to that when girls were first offered the vaccine (87.5%). The planning of the second dose coincided with the first COVID-19 lockdown, which could have impacted its coverage.