Does Vaccine Hesitancy Matter?

A friend asked me this week if it really matters if other people delay vaccinating their children.  As long as their child has received at least one dose of each vaccine, they asked, isn't their own child protected?

Absolutely not!  For one, most vaccines require multiple doses for full effect; for another, even the best vaccine is not completely effective.  The current pertussis vaccine, developed because of worrisome but not dangerous reactions to the cellular vaccine, is only about 85% effective.

Let's take measles FOR EXAMPLE. Modeling - based on lots and lots of data- shows that for one, about 95% of the population needs to be vaccinated to prevent outbreaks.  Here is a particularly good REAL WORLD EXAMPLE of what happens, in a densely populated area, when this isn't the case.  You can read the whole paper for yourself, but the summary is: not twelve years ago, the Solomon Islands had a big measles outbreak.  There were only 50,000 people living on the islands and at least 800 of them caught measles.  The outbreak lasted six months.  Six months.  They finally went and re-vaccinated 35,000 people regardless of whether they'd previously been immunized.

Take that in for a minute.  They re-vaccinated 70% of the population.

"From 1989 until 2003, the RMI did not report a single case of measles, and World Health Organization (WHO) cluster surveys showed single-dose vaccine coverage of 93% and 80% among 2-year-old children in 1998 and 2001, respectively, although second-dose coverage lagged behind at 40% in both years." 

"The outbreak ended only after vaccination of ~35,000 persons among a population of 51,000." 

"[T]he reported coverage of 1-dose measles-mumps-rubella (MMR) vaccine was 80%–93%..... [Of the measles cases] (23% involved infants who were below the age of routine vaccination), 100 hospitalizations (34% involved infants), and 3 deaths. Of outbreak cases, 41% were reported to have been previously vaccinated." 

That's right! This large outbreak happened even to people who had been vaccinated. The percent of the population dropped below the protecting-everyone threshold- in part because many children did not receive their vaccines on time, especially the second dose!

Why stick to the recommended schedule?  Because in general, there have been lots and lots of studies demonstrating to test the schedule and determine what sequence gives the best immunity - while protecting children as much as possible.  In other words, vaccines are given as soon as it's been shown they'll be both safe and effective in children of that age.

Whenever someone, because they read a dumb book or heard someone on the radio or for any other not-medically-indicated reason, delays their child's vaccines, they are increasing the chances of an outbreak.  Infants are disproportionately vulnerable in outbreaks - but also even children old enough to be vaccinated are at higher risk.  They're putting your kids at risk, but they are also putting their own kids at risk.  Please, tell them.

Have you ever convinced someone to vaccinate their child in a more timely fashion? Or informed them of FACTS about vaccines?  Told them a personal story ('my cousin got pertussis and gave it to my grandma')?

(Retrospective irony alert: "In contrast, (less than) 120 measles cases have occurred annually in the United States since 1998 [2, 3]. The success of the US measles program is based on (greater than) 90% preschool vaccination coverage for 1 dose of measles vaccine and the near-universal requirement of a second dose for school entry [4–6].