The findings come from two new reports, one looking at data collected from WHO's Global Surveillance and Monitoring System over the last four years and another that pooled data from 100 literature reviews to examine the public health and socioeconomic impact of substandard and falsified medicines.
Based on the reports, WHO says that as many as one in 10 medicines sold in low- and middle-income countries is either substandard or falsified, at a cost to the global health system of $30 billion per year.
"Substandard and falsified medicines particularly affect the most vulnerable communities," said WHO Director-General Tedros Adhanom Ghebreyesus, who called on countries to take "tangible action" to address the issue.
"Many of these products, like antibiotics, are vital for people's survival and wellbeing," said Mariângela Simão, assistant director-general for access to medicines, vaccines and pharmaceuticals at WHO.
Antibiotics and antimalarial drugs account for more than one-third of all products reported to be fake or substandard to WHO. Fake versions of such drugs can lead to prolonged illness or death, while substandard versions can lead to increased drug-resistance.
Based on the estimates gathered in the reports, the University of Edinburgh says that between 72,000 and 169,000 children die of pneumonia each year as a result of taking substandard and falsified medicines, while a model developed by the London School of Hygiene and Tropical Medicine finds that such products lead to an additional 116,000 deaths from malaria each year in sub-Saharan Africa alone.
In the four years since launching its Global Surveillance and Monitoring System, WHO says it has received more than 1500 reports of substandard or falsified medicines, with 42% of reports coming from sub-Saharan Africa, and 21% each coming from the Americas and Europe.
The agency also says it suspects underreporting from some regions, as only 8% of reports came from the Western Pacific, 6% from the Eastern Mediterranean and only 2% from South-East Asia.
According to Suzanne Hill, director of WHO's Department of Essential Medicines and Health Products, authorities around the world must step up their efforts to raise awareness about the dangers of substandard and falsified medicines and work to stop such products from entering the supply chain.
To do so, Hill says that countries must have effective border control, rapid reporting of suspected spurious products, risk-based inspections and postmarket surveillance, as well as access to laboratories and screening equipment.
"Without strong regulatory capacity and systems in place we will not see a resolution to the problem, but we also need sound investment in safeguarding the manufacture, distribution and supply of medical products," Hill said.