The solution in many European countries — to stop using seemingly riskier vaccines in younger people, who are at lower risk from Covid-19 — would be unworkable in Africa, where the median age in many countries is below 20.
And any further restrictions would compound the hurdles facing Covax, among them a paucity of funding for every part of inoculation programs beyond the touchdown of doses at airports.
Mali, in western Africa, has administered 7 percent of the AstraZeneca doses that Covax has delivered. Sudan, in eastern Africa, has given 8 percent of the doses it has received.
Skittishness over the AstraZeneca and Johnson & Johnson vaccines, analysts fear, could stoke demand for Russian- and Chinese-made shots about which far less is known. As it is, some global health officials have turned their attention to the Novavax vaccine, which is not yet authorized but makes up a third of Covax’s portfolio.
“Even at this stage of the pandemic, we have our fingers crossed that some vaccine will work to help vaccinate developing countries, instead of ramping up production of vaccines we know work,” said Zain Rizvi, an expert on medicines access at Public Citizen, an advocacy group.
In Kenya, where enthusiasm for vaccines is high in cities but perilously low in rural areas, “the story about blood clots from Europe could not have come at a worse time,” said Catherine Kyobutungi, the director of the African Population and Health Research Center there. “Even those who were perhaps on the fence, and leaning toward getting vaccinated, all of a sudden had second thoughts,” she said.
The American pause on Johnson & Johnson shots promised a second media furor.
“When the F.D.A. suspends, it makes headlines for days,” she said. “When it lifts the suspension, it doesn’t make as many headlines.”
Mady Camara contributed reporting from Dakar, Senegal.
