Pregnant Hong Kong women show no significant drop in hepatitis B prevalence rate despite vaccinations, study finds
Screening of pregnant women and students suggests effectiveness declines over time, according to Chinese University study
PUBLISHED : Tuesday, 28 April, 2015, 4:16pm
UPDATED : Wednesday, 29 April, 2015, 1:15am
There has not been a significant drop in the number of pregnant women with hepatitis B despite the introduction of a vaccine 27 years ago, research has found.
Chinese University researchers also revealed that older women were more at risk from the infectious liver disease, which suggested the vaccine became less effective with age. They called for routine screening and booster doses for new health workers, who are considered to be at high risk of exposure.
Vaccines against hepatitis B have been given to babies - at birth, at one-month old and at six months - city-wide since 1988. However, the team found that the prevalence rate among pregnant women - the only group routinely screened for the disease - hovered around 10 per cent between 1998 and 2010, with at most a single percentage point change from the average.
The rate rises with age. In a study of 10,808 mothers aged 16 to 25 from 1998 to 2011, the rate increased from 2.3 per cent for 16-year-olds to 7.9 per cent among 25-year-olds.
Protection given by vaccines might decline over time. Five years after the vaccine, people usually test negative for antibodies that protect against the virus. But, if the vaccine is effective, antibodies should return on infection, due to what researchers call "immune memory".
"People who worry about the risk of infection should take a three-dose booster to get full protection," said Professor Paul Chan Kay-sheung, of the university's microbiology department.
Researchers stressed vaccines at birth were still useful.
The Department of Health said it was routine practice to screen public sector health workers. But it did not see the need to offer routine boosters.
Researchers think social habits might also increase risk. Sex, having tattoos, ear-piercing and sharing food utensils can all transmit the virus.
This article appeared in the South China Morning Post print edition as Vaccines at birth fail to halt hepatitis B