He said the differences were not necessarily a problem, but the issue lay in the fact that the data on the Chinese and Russian vaccines is incomplete, as doses began to be administered before trials finished or approvals granted.
The WHO has so far only licensed the Pfizer/BioNTech jab and the Oxford University/AstraZeneca shot, both developed in Europe, although the European Medicines Agency is now assessing the Russian vaccine, Sputnik V.
“Without access to more proven vaccines, and being unwilling to wait for wealthy nations to donate vaccines, middle-income countries in particular are turning to less proven vaccines,” said Mr Bollyky.
The effectiveness of the different jabs is also an issue, experts said, and there is a feeling that richer countries were getting “better”, often more expensive vaccines, like Pfizer’s, which had efficacy rates of 95 per cent in clinical trials.
While Russia’s Sputnik jab has reported similar results, recent data from Brazil on China’s Sinovac jab showed an efficacy rate of just over 50 per cent at preventing symptomatic infection, although results from other countries were more promising.
Agathe Demarais, global forecasting director at The Economist Intelligence Unit who has also been tracking vaccine diplomacy, said: “This is actually increasing the resentment – it makes it look like rich countries have access to the best vaccines whereas others do not.”
She added: “They are trying to bolster their standing in emerging countries, betting on the resentment of greedy rich Western countries keeping the vaccines for themselves.
“Russia and China are trying to present themselves as the saviours of the developing world, but it’s not just about that – it’s about having a long-term influence on the ground.”
And it is easy to see where Russia and China are targeting, said Mr Bollyky.
“We are definitely seeing vaccines going to countries of interest – neighbours, nations with natural resources or geopolitical interest – as opposed to where the crisis is currently the largest,” he said.
Ms Demarais said that digging into the data showed differing approaches in different countries, depending on their strategic importance.