Cer­vi­cal can­cer vac­cine might be ef­fec­tive af­ter just 1 shot rather than rec­om­mended 3

The China Post - - LIFE - BY MARIA CHENG

Pro­tect­ing girls from cer­vi­cal can­cer might be pos­si­ble with just one dose of the HPV vac­cine rather than the three now rec­om­mended, a new anal­y­sis sug­gests.

The au­thors of the study ac­knowl­edged it isn’t con­vinc­ing enough to change vac­ci­na­tion strate­gies im­me­di­ately. But if their re­sults are con­firmed, re­quir­ing just one dose of the vac­cine could have a big im­pact on how many girls around the world get im­mu­nized.

Cer­vi­cal can­cer is the fourth-most com­mon cause of can­cer death in women world­wide and is es­ti­mated to kill more than 260,000 ev­ery year.

Re­searchers from the U.S. Na­tional Can­cer In­sti­tute and else­where looked at data from pre­vi­ous tri­als cov­er­ing more than 24,000 young women to see how much pro­tec­tion they got from one, two or three doses of the HPV vac­cine, Cer­varix. They es­ti­mated vac­cine ef­fec­tive­ness af­ter about four years to be be­tween 77 per­cent and 86 per­cent for all the young women, re­gard­less of how many shots they re­ceived.

If fewer doses could be used, “the po­ten­tial is huge to pre­vent the deaths of mil­lions of women,” said Ju­lia Brother­ton, med­i­cal direc­tor of the Na­tional HPV Vac­ci­na­tion Pro­gram Reg­is­ter in Australia.

The study was paid for by the U.S. Na­tional Can­cer In­sti­tute and oth­ers in­clud­ing the vac­cine’s maker, Glax­oSmithK­line PLC. It was pub­lished on­line Wed­nes­day in the jour­nal Lancet On­col­ogy.

Brother­ton au­thored an ac­com­pa­ny­ing com­men­tary and said in an email the re­sults were “re­ally promis­ing and so strong that it is dif­fi­cult to imag­ine” there could be a con­found­ing fac­tor to ex­plain the find­ing. She said it wasn’t clear why one dose ap­peared to be so ef­fec­tive, but sug­gested the “virus-like” par­ti­cle used to make the vac­cine might have pro­voked a par­tic­u­larly strong re­sponse from the girls’ im­mune sys­tems.

Be­sides Glaxo’s Cer­varix, a sim­i­lar vac­cine, Gar­dasil, is sold by Merck & Co. It’s un­clear if that vac­cine would also work with fewer doses, although ex­perts said that was pos­si­ble since Gar­dasil is also made with virus-like par­ti­cles.

Glaxo wel­comed the find­ings but said in a state­ment “at this time, we have no plans to file for a sin­gle-dose li­cense.”

In Bri­tain, health of­fi­cials changed their rec­om­men­da­tion last year to ad­vise young girls only get two doses of the HPV vac­cine in­stead of three.

In the U.S., no HPV vac­cine is li­censed as a two-dose reg­i­men and the top vac­cine ad­vi­sory com­mit­tee hasn’t dis­cussed data from us­ing only one dose. Young girls typ­i­cally start get­ting vac­ci­nated around age 11 to 12 and each dose of the HPV vac­cine costs about US$100.

Aimee Kreimer of the U.S. Na­tional Can­cer In­sti­tute, one of the study’s au­thors, said de­ter­min­ing how long girls would be pro­tected with a sin­gle dose was es­sen­tial.

“The vac­cine will need to pro­vide at least 10 years and ide­ally 20 years of pro­tec­tion against cer­vi­cal HPV in­fec­tions to have the great­est im­pact of re­duc­ing cer­vi­cal can­cer,” she wrote in an email.

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