But profit margins are hard to know, as R&D (which can take up to 15 years), manufacturing, trials to test efficacy, and distribution costs for specific vaccines and drug products are not public. While a spokesperson for Merck told The Atlantic that vaccines remained one of its key areas of focus—it generated $5.3 billion in sales in 2014—she did not comment on the profit margins. Analysts peg the profit margin of giant pharmaceutical companies at anywhere ranging between 10 to over 40 percent. “Nobody knows exactly how much it costs for them to make it, because they don’t want to reveal that,” says Halsey. They fear that they would face pressure to lower prices in the U.S., Europe, and the developing world.

And costs are an issue: Where there were once worries that low vaccine prices would drive manufacturers out of the market and lead to shortages, there are now worries that prices are too high for both the developed and developing world. The New York Times reported last year that some American families had trouble finding doctors for vaccine administration because the vaccines were too expensive for doctors to stock. Doctors Without Borders recently called for Pfizer and GlaxoSmithKline to lower vaccine prices for developing countries.

In response to calls for vaccine costs to come down, supporters of increasing vaccine supply such as Bill Gates have argued that not only is vaccine production very complicated, but research and development budgets would suffer. While the pharmaceutical industry is unlikely to budge on revealing their profits, Halsey suspects that having more manufacturers would help lower prices. Yet the vaccine market is highly concentrated on both the supply and demand side, with high fixed costs and exclusive licensing discouraging competition.

So while the vaccine industry is likely more profitable now than in the 1970s or 1980s, this is the result of global market forces, not a reason to skip a child's vaccinations: Pharmaceutical companies need incentives to keep producing vaccines, because regardless of profits the economic and social benefits of vaccination are huge—in lives and the billions of dollars saved. A study released last year estimated that fully immunizing babies resulted in $10 saved for every dollar spent, about $69 billion total. "Vaccines are one of the most cost-effective interventions we have," says Halsey.

In the U.S., a study looking at the benefits of vaccination between 1994 and 2013 estimated a net savings of $295 billion in direct costs and $1.38 trillion in total societal costs. Looking at the last 50 years of the vaccine market, it's absurd to think profits could have ever been the sole motivation of vaccine production. In fact, 83 percent of Americans believe that the MMR vaccine is safe. Profits from vaccine production aren't a valid argument against vaccinations—the most important question is whether vaccines are safe and effective, and the answer is unambiguously yes.

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