270.41 mln doses of covid-19 vaccines have been done on May 1,in China

With little data released internationally, the effectiveness of the various Chinese vaccines has long been uncertain.

Brazilian trials of the Sinovac vaccine CoronaVac for instance, showed an efficacy rate of around 50.4%, which is barely over the 50% threshold needed for regulatory approval by the World Health Organization (WHO).

So far, Sinovac's CoronaVac jab has only been fully authorised for use by China.

But Beijing is also offering its vaccines around the world and has already shipped millions of doses to a number of countries.

In Asia, the biggest takers are Indonesia, Malaysia, the Philippines, Thailand and Pakistan, while in the Americas, Brazil, Mexico, Chile, Colombia and Ecuador have also ordered millions of shot.

In Europe, Turkey and Ukraine have signed large contracts for CoronaVac.

The vaccine is thought to be particularly important for African countries where so far Zimbabwe, Somalia, Djibouti, Benin and Tunisia have received vaccines from China.

hina's vaccines though differ significantly from some vaccines, especially those developed by Pfizer and Moderna.

Developed in a more traditional way, they are so-called inactivated vaccines which means they use killed viral particles to expose the immune system to the virus without risking a serious disease response.

By comparison, the BioNtech/Pfizer and Moderna vaccines are mRNA vaccines. This means part of the coronavirus' genetic code is injected into the body, training the immune system how to respond.

The UK's AstraZeneca vaccine is yet another type of vaccine where a version of a common cold virus from chimpanzees is modified to contain genetic material shared by the coronavirus. Once injected, it teaches the immune system how to fight the real virus.

One significant advantage of the Chinese vaccines is that they can be stored in standard refrigerators at 2-8 degrees Celsius. Moderna's vaccine needs to be stored at -20C and Pfizer's vaccine at -70C.