New Gardasil 2-Dose Series: A Pair Equals 3-of-a-Kind

December 9, 2016
Terry Brenneman, MD
Terry Brenneman, MD

"My child won't be intimate before marriage," is a common parental refrain. The CDC says, don't bet on it. Do you know the odds?

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Casino owners love their slot machines. Minimum payouts vary by state law. In Nevada, for instance, that number is 75% which means that, on average, a machine will return 75% of the money put into it. The house edge in blackjack, for comparison, is under 1%. Playing the slots is a “sucker bet.”

Parents have been known to make “sucker bets” with their child’s health. “My child got the flu vaccine last year and got the flu anyway, so I don’t want him to get vaccinated this year,” is a comment I occasionally hear. Right, flu vaccines aren’t perfect and every year’s efficacy is different.  Some years, the efficacy is under 50%, but even a vaccine with 33% efficacy is better than no vaccine at all-with an efficacy of 0%.

Another comment I hear relates to HPV vaccine Gardasil:  “My child doesn’t need it since (s)he isn’t going to have sex until marriage.” CDC data suggests this, too, is a sucker bet.

According to the CDC’s annual survey on risky behaviors in youths in 2015, which of the following is/are true?

A. By 12th grade, 90% of students have had sexual intercourse

B. By 12th grade 58% of students have had sexual intercourse

C. Before age 13 years, less than 2% of males and females have had intercourse

D. Before age 13 years, 2.2% of females and 5.6 % of males have had sexual intercourse

Answer and discussion>>

 

Answers. B and D are true (58% of students have had sexual intercourse by 12th grade and 2.2% of females and 5.6% of males have had sexual intercourse before the age of 13 years.

Did (s)he say "Yes?"

Another risk I mention to parents is that not all sex is consensual. The CDC survey found that 11% of students who date reported being forced to do a sexual “thing” in the 12 months preceding the survey. I also will usually tell these parents that, “I support your strong family values. It is important to let your children know where you stand. At the same time, if your child’s eventual spouse had even just one indiscretion, then (s)he may infect your child on their wedding night and that could lead to cancer.”

Pair beats 3-of-a-kind

Poker players know that three-of-a kind always beats a pair, but not so for HPV vaccines anymore. The CDC recently announced that a pair of HPV vaccines is as good as the previously recommended 3-dose series. Two caveats: 

 - First, the initial dose must be given before the 15th birthday; and

 - Second, the minimum interval between the two doses should be at least 6 months.

Most European countries and the World Health Organization switched from a three- to a two-dose series in certain scenarios in 2014. The CDC does not have efficacy data on this 2-dose series; the decision is based on the level of antibody production which is higher in the younger ages.

Two questions may come up that were not specifically addressed in the new recommendations. If an adolescent gets his first dose under the age of 14 and 6 months and is now older than 15, will he need one or two more doses?  The way I read the new directive, he would only need one, even if years have passed. The second question relates to the interchangeability between the bivalent (Cerverix) and nonavalent (Gardasil). Previously, the CDC did feel these vaccines were interchangeable, meaning that one could use either of the available vaccines in completing the 3-dose course. Will that apply to the two- dose series?  I suspect it will, but it will be a decision based on “expert medical opinion” rather than any hard data at this time.

I am excited for this change to a two-dose series for several reasons. First, my percentage of patients who have completed the recommended schedule just went up without me having to do a thing. More importantly, this change will help me, I hope, in convincing parents to agree to start the series at the recommended 11- to 12-year age range. As noted above, about 1 in 20 boys by the age of 13 years has already had sex and possibly been infected with HPV. Don’t make a sucker bet with your child’s life at stake.

 

Interesting Reading

House odds for a variety of casino games. Guess what? They all favor the house.https://wizardofodds.com/gambling/house-edge/

This 174-page CDC annual survey looks at a multitude of risky behaviors (drugs, vaping, texting while driving, sex, etc) broken down by states. It is amazing anyone reaches adulthood. http://www.cdc.gov/healthyyouth/data/yrbs/pdf/2015/ss6506_updated.pdf

This slide show on HPV was presented at the ACIP meeting that lead to the approval of the Gardasil two-dose series.https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2016-02/hpv-02-markowitz.pdf 

The new CDC position on the HPV vaccine schedule. http://www.patientcareonline.com/vaccines/new-gardasil-2-dose-series-pair-equals-3-kind/page/0/2