The issue of the role of intermediates for buying vaccines was raised recently as a middleman, located in the United Arab Emirates, was caught selling Sputnik vaccines to Ghana and Pakistan at double the original price.
Simao said that countries should either buy directly from the manufacturer or "contact the manufacturer to make sure that the intermediate is legal."
"There is a lot of substandard and falsified COVID products being commercialized out there, so you need to know the provenance," she added.
Simao also said that it was important to vaccinate people with products "certified" by the WHO.
"The advice of the WHO is that the countries use vaccines that have received emergency listing," she said, referring to the Emergency Use Listing used by the organization to approve new vaccines.
So far, eight COVID-19 vaccines were approved by the WHO for emergency use, including two Chinese vaccines -- Sinopharm and Sinovac, both of which have been distributed in several countries across the world.