Filed under: CDC Watch, Opinion, Vaccine Science, Vaccine/Disease Analysis
A handful of countries recommend the chickenpox (varicella) vaccine for all children and an even smaller group have a chickenpox booster on the schedule. The US leads the pack of countries with a 2 shot schedule, and following along are Ecuador, Saudi Arabia, Germany, Greece, and part of Australia.
Some countries give the shot to adolescents, others offer it to members of “risk groups”… and a few have a one-shot schedule for toddlers: Canada, Costa Rica, Uruguay, Cyprus, Latvia, and Korea. A grand total of 26 countries offer the shot in one way or another. 
The US was the first country to recommend the shot for all toddlers, in 1996 :
…. empiric data on medical utilization and costs of work-loss resulting from varicella were used. The results of this study, which were determined using an estimated cost of $35 per dose of vaccine and $5 for vaccine administration, indicated a savings of $5.40 for each dollar spent on routine vaccination of preschool-age children when direct and indirect costs were considered. When only direct medical costs were considered, the benefit-cost ratio was 0.90:1.  (emphases added)
But it turned out that a single shot of varicella vaccine didn’t work to suppress chickenpox.
…varicella outbreaks have regularly been observed in populations with high vaccination coverage and are the cause of sizable disease and economic impact for public health departments and the US health system overall. To further reduce varicella disease burden, a routine 2-dose varicella vaccination recommendation was approved by the Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) in June 2006 (first dose for children 12–15 months of age, second dose for children 4–6 years of age) . 
The single-shot regimen showed a narrow margin of benefit only when placed alongside income lost by parents staying home to care for sick children.
But when the one-shot program failed, the ACIP came up with another cost/benefit justification for the second shot where the evidence….
….included ongoing disease burden and varicella-zoster virus transmission, including transmission from breakthrough cases to high-risk persons that may lead to severe disease and even death (CDC, unpublished data); partial or complete susceptibility in 1-dose vaccine recipients as they become adults; the burden on public health agencies due to varicella outbreaks in highly vaccinated school settings, which have proven disruptive to society and costly to control; and the increased immunity and disease protection from a second dose. Overall, the 2-dose strategy still provides very high cost savings (>$0.9 billion from societal perspective).  (emphases added)
So the ACIP justifications for adding a second dose, used the consequences of their decision to recommend the first dose of varicella vaccine. These ingenious calculations created a bigger cost savings than their first round! Read more