Vaccines based on mRNA need to get out of the freezer

The first successful attempt to transport vaccines over long distances was crude, but ingenious. In 1803, seven years after Edward Jenner’s demonstration that inoculations of the lymph from cowpox pustules could protect against smallpox, a group of 22 orphan boys embarked in La Coruña on a ship bound for Spain’s American colonies. Two had been deliberately infected with cowpox. When they developed pustules Francisco Xavier de Balmis y Berenguer, the doctor who had organised the expedition, used the lymph therein to inoculate two more. And so on, until the ship arrived a little over two months later and inoculations could be given to locals.It was a splendid success. Thousands of people across the empire, as far north as Mexico, as far south as Peru and (after a further expedition crossed the Pacific) as far west as the Philippines, were vaccinated. Even today, though using orphans for them is now discouraged, the concept of vaccine-preservation chains lives on, with “cold chains” of refrigerators or freezers being employed routinely to preserve heat-sensitive material that is being moved from place to place.