The lack of vaccine education plays into an underlying mistrust of many medical treatments, especially those that come from other countries. That mistrust has its roots in a history of horrific experiments under colonialism.

In present-day Namibia during the early 1900s, German officials sterilized some local residents, injected others with arsenic and deliberately infected people with smallpox, typhus and tuberculosis (as this Times essay by Kavena Hambira and Miriam Gleckman-Krut explains).

Such direct harm became less common in the second half of the 20th century, but mistreatment was still common. Drug companies sometimes conducted research trials without people’s consent. Only a decade ago, Pfizer made financial payments to the parents of dead children in Nigeria after a research trial went wrong.

Arguably the biggest source of modern distrust in southern Africa is H.I.V. After inventing lifesaving treatments, Western pharmaceutical companies initially kept their prices too high for many Africans to afford, and governments did not fix the situation for years.