section_path: History/2021
section_name: 2021
paragraph_text: 2021
  
  On 2 January, the Alpha variant, first discovered in the UK, had been identified in 33 countries. On 6 January, the Gamma variant was first identified in Japanese travellers returning from Brazil. On 29 January, it was reported that the Novavax vaccine was 49 per cent effective against the Beta variant in a clinical trial in South Africa. The CoronaVac vaccine was reported to be 50.4 per cent effective in a Brazil clinical trial.
  
  On 12 March, several countries stopped using the Oxford–AstraZeneca COVID-19 vaccine due to blood clotting problems, specifically cerebral venous sinus thrombosis (CVST). On 20 March, the WHO and European Medicines Agency found no link to thrombosis, leading several countries to resume administering the vaccine. In March WHO reported that an animal host was the most likely origin, without ruling out other possibilities. The Delta variant was first identified in India. In mid-April, the variant was first detected in the UK and two months later it had become a full-fledged third wave in the country, forcing the government to delay reopening that was originally scheduled for June. On 10 November, Germany advised against the Moderna vaccine for people under 30, due to a possible association with myocarditis. On 24 November, the Omicron variant was detected in South Africa; a few days later the WHO declared it a VoC (variant of concern). The new variant is more infectious than the Delta variant.