$2 billion agreement part of Trump program in which multiple vaccines are developed simultaneously, with goal of delivering 300 million doses by January

Researcher says those given booster developed dual reactions: 'There's increasing evidence that having a T-cell response as well as antibodies could be very important'

Deal for inoculations with US biotech firm Moderna said to not include means to inject vaccine; official warns mass purchase of syringes is vital

Controversial 'pre-testing' move by SinoPharm raises ethical questions, coming before vaccine had government approval for trials in people

Researchers in Britain, US, Canada said targeted as London vows 'to hold perpetrators to account'

Renewed virus rules take effect in Hong Kong; Melbourne residents are warned of possible lockdown; South Korea says contact tracing increasingly hard as more people go out

Vaccine shown to provide immune boost in 45 volunteers; 'No matter how you slice this, this is good news,' says Dr. Anthony Fauci, US government’s top infectious disease expert

Gavi group, which provides vaccines to children in poor countries, under fire for promising donor governments doses for 20% of their population

Research on 90 patients, healthcare workers at London hospital finds that 60% had 'potent' antibody response when infected, but it was only maintained in 17% of them 3 months later

Epidemiologist Arnaud Fontanet says people have to learn to live with virus and urges public to to take social distancing measures more seriously