Various companies use different ingredients and different delivery systems in their COVID-19 vaccines. Researchers are investigating whether it's better for individuals to mix what's available.
Sixteen countries authorised the use of Russia's Sputnik V vaccine before phase 3 clinical trial results were published.
While Serbia's Covid-19 infection rate continues to be worrisome, the country has shown the ability to vaccinate a higher proportion of its population than EU nations.
The COVID-19 vaccination programme requires stringent data collection and transparency.
Britain moves to protect itself from the B1617 variant, which vaccines may be less effective against.
It's cheap and easy to store, but the Russian vaccine does not yet have approval in Europe.
The global vaccine rollout has not been free from geopolitical rivalries and point-scoring.
Vaccines that use harmless viruses as a delivery mechanism are vulnerable to being attacked by our immune system – but experimenting with how they are given could get around this.
With richer countries having bought up most of the leading western vaccines, others are looking to India, China and Russia for supplies.
Early data shows that vaccines work for older people who are more at risk of severe COVID-19.
Another day, another politicised vaccine.