A new study is urging blanket hepatitis B vaccinations for Ontario newborns and better screening for pregnant women who may unknowingly spread the virus.
Children in Ontario and several other provinces don't get their hep B shot until Grade 7, but research published in the Canadian Medical Association Journal suggests earlier vaccinations could help avoid the spread of hundreds of infections.
Analysis of provincial data between 2003 and 2013 found 139 Canadian-born children under the age of 12 with the virus. Researchers suspect the number is actually higher because most kids are never tested, and few display symptoms.
Meanwhile, study co-author Mia Biondi says separate data shows 62 per cent of pregnant women who test positive are not further tested to see if antivirals could prevent transmission to their baby.
“We're clearly missing these intervention points,” says Biondi, a researcher at the Toronto Centre for Liver Disease and a nurse practitioner in the community.
“Hopefully this will initiate a conversation with the province about possibly changing our vaccine strategy.”
How transmission happens between mother and child is not well understood but likely occurs in the third trimester, during labour and delivery, or in the first few months of life, says Biondi.
She says mathematical modelling suggests about 450 women over a five-year period might have needed antivirals during pregnancy but didn't get it, although researchers don't know it those women actually passed hepatitis B to their children.
Biondi says the findings make a strong case for hep B vaccination at birth, or that it be integrated with the vaccinations routinely given to babies at the two-month mark.
Hepatitis B is highly infectious, especially for children younger than five. Biondi says more than 90 per cent of young children who contract it go on to suffer chronic infection, putting them at high risk of cirrhosis and liver cancer.
However, only five to 10 per cent of adolescents who contract hep B develop chronic conditions because of their more developed immune systems, says Biondi.
“So this idea that we're immunizing adolescents at a time where they're even less likely to go on to become chronic anyways, whereas children are very likely to go on to become chronic, might be a little bit backwards,” says Biondi.
It's important to make sure children receive the vaccine before they become sexually active because the virus spreads through infected bodily fluids, says Biondi, but another issue is that uptake at adolescence can be low.
The study notes that average vaccination coverage among 12-year-olds was 70 per cent from 2013 to 2018, with some public health units reporting rates as low as 50-to-60 per cent in 2017-2018.
The World Health Organization recommends vaccination against hep B at birth, however only New Brunswick, Northwest Territories and Nunavut do this in Canada.
Several provinces start vaccinating at two months, including British Columbia, Quebec, Prince Edward Island, and the Yukon.
Saskatchewan, Manitoba, Nova Scotia and Newfoundland and Labrador also don't offer the hep B vaccine until grades 6 and 7.
Alberta used to wait until Grade 6, but since March 2018 has offered shots to infants at two months old.
Biondi says vaccinating at birth is particularly important because of Canada's relatively high number of immigrants from regions where hep B is endemic.
She says this would protect infants if maternal screening is missed, but also protect them from other contacts who may not know they are infected.
The CMAJ study was published Monday.