More countries are dropping the number of doses needed for HPV vaccines. Should Canada?
Single dose just as effective in preventing infections, multiple studies suggest
Starting this fall, teens in England will get just one HPV shot — making it the latest country to drop the number of required doses for the highly effective vaccines known for protecting against a slate of cancers.
The World Health Organization (WHO) announced more than a year ago that a single dose delivers "solid protection" against human papillomavirus (HPV) that's comparable to two or three shots, based on a growing body of global evidence. Ireland, Scotland, Wales and Australia have already made the switch. And many researchers say providing fewer doses can free up much-needed resources for other public health efforts.
So, should Canada follow other countries' lead by taking a one-dose approach? There's no decision here just yet.
The country's top vaccination advisers are looking at "all the available evidence" while conducting their own analysis based on Canadian disease rates and modelling projections, a spokesperson for the Public Health Agency of Canada told CBC News. That work is "expected to be finalized next year."
Currently, Canadian guidelines suggest that healthy kids aged nine to 15 should get one of the available HPV vaccines on either a two or three-dose schedule.
The current chair of Quebec's immunization committee, Dr. Caroline Quach — who chaired the National Advisory Commitee on Immunization (NACI) during much of the COVID-19 pandemic — is among the Canadian medical experts who say Canada should consider following the lead of England and other countries.
One dose effectiveness 'quite high'
"When you look at the studies that have been published worldwide ... the effectiveness of one dose of the HPV vaccine is actually quite high," Quach said.
"In terms of prevention of HPV infections that may lead to cancer, whether you give one dose or two doses basically gives you the same amount of protection."
Research from India and Costa Rica has shown the durability of one dose of certain types of HPV vaccines lasts a decade, noted the U.K.'s vaccine advisory committee.
The U.K. also looked at a more recent trial in Kenya, which was also meant to study the effectiveness of a single dose. That research found young girls and women were effectively protected from HPV infection for 18 months post-vaccination — with vaccine efficacy at more than 97 per cent, keeping the results in line with trials for three doses.
"Every country and every advisory committee needs to review the data and look at the modelling, the epidemiology of their own country," Quach said. "But it's absolutely something that we have to look at."
Dawn Bowdish, an immunologist at McMaster University in Hamilton, said she feels a cautious approach is more prudent, to gauge whether a reduced number of required doses maintains decades-long protection.
Most childhood vaccines need multiple doses to sufficiently train the immune system to recognize a threat in the long term, she added. And even with less HPV circulating now in Canada thanks to years of HPV vaccination efforts, she said the country remains in a "delicate spot."
"The tide can turn very quickly if we lose the advantage of vaccination," Bowdish warned. "We haven't eliminated this virus — it is ready to come back and find vulnerable people again."
Quach, however, stressed that if Canada goes the one-dose route, robust surveillance programs would pick up early warning signs if the approach falls short, suggesting the country should reverse course and offer catch-up shots.
And both agree there's a key element to the entire discussion around the ideal number of doses: money.
"The gamble that the U.K. is making is that one dose will be sufficient ... but they felt that the cost benefit was worth it," Bowdish said. "It would be cheaper to administer one dose, and easier than getting someone to come back three times."
The resources freed up from the upcoming move to one dose can be redirected, "improving our already high vaccine coverage levels and ensuring that anyone who misses their dose still has other opportunities to receive it," Mark Jit, an epidemiologist with the London School of Hygiene & Tropical Medicine in England and a member of the Single Dose HPV Vaccine Consortium, said in a statement.
On a global level, advocates also say that lowering the number of needed doses could be a massive cost-saving measure for vaccinating populations in lower- and middle-income countries.
High costs for adults who want the shots
But what the shift wouldn't solve here in Canada are the sky-high costs adults face when they age out of government vaccination programs.
In Ontario, for instance, students in Grade 7 can get the HPV vaccine for free. Public health clinics also typically offer the shots for free to students up to Grade 12, and gay, bisexual and trans men up to the age of 26.
Other young adults who want the shots, but aren't eligible for free programs, can spend roughly $600 on three required doses, said London, Ont., resident Gillian Cameron, an advocate for broader HPV vaccine access. (The vaccines can be purchased privately with a prescription, and may be covered by some insurance providers.)
Cameron is now calling on the Ontario government to provide free HPV shots to everyone under the age of 26 — and more than 30,000 people have signed her online petition so far.
"It was kind of a question, like, are you going to pay for your phone bill this month? Are you going to pay for groceries? Or are you going to get this vaccine?" she said.
That's a choice no Canadian should have to make, Cameron added, given the overwhelming evidence that these shots save lives by preventing infections that can lead to potentially deadly cervical, anal, and head and neck cancers.
An HPV vaccine was first recommended in the U.S. back in 2006, and in the 10 years following, quadrivalent type HPV infections decreased by 86 per cent in female teens aged 14 to 19 years, and more than 71 per cent in women in their early 20s, the U.S. Centers for Disease Control and Prevention says.
And on the cancer front, a U.K. study published in the Lancet in 2021 found cervical cancer rates were 87 per cent lower in young women who had been eligible for HPV vaccination when they were aged 12 to 13 years, compared with young women who had not been offered vaccination.
While NACI continues assessing the ideal number of doses, there is international consensus regarding the astounding overall success of these vaccines.
"The fact that we have a vaccine that can prevent cancer ... how amazing is that?" Bowdish said.
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