There were only nine cases of COVID-19, and they all happened in the placebo group.
"Our findings extend those from smaller studiesreported elsewhere and support a potential strategy of providing a single dose of vaccine to persons with a confirmed prior history of coronavirus infection, along with two doses for people not previously infected", said Susan Cheng, Associate professor at the Cedars-Sinai Medical Centre in California, US.
The part of the trial from South Africa involved 800 participants. "These data also provide the first clinical results that a vaccine can effectively protect against now circulating variants, a critical factor to reach herd immunity and end this pandemic for the global population".
The latest figures from Africa CDC showed that as of Friday, the number of confirmed Covid-19 cases in Africa has reached 4,239,639, and the death toll from the pandemic stood at 113,142, while 3,794,269 patients have recovered.
Jacy Smith, of Shirley, says she thinks these updated guidelines will also make more people want to get vaccinated.
Australia's Brisbane lifts snap virus lockdown ahead of Easter Premier Annastacia Palaszczuk said she would raise the high numbers of overseas-acquired cases in national cabinet next week. Queensland Health have meanwhile said Anzac Day events will go ahead in the state on April 25 as long as they are Covid-safe.
The state travel advisory also says nonessential travelers who don't get tested should self-quarantine for 10 days after travel.
The study found cellular T cell responses developed in 63% of the older people given two doses of the Pfizer jab.
'These mRNA vaccines - it really seems the level of antibodies they elicit are so high, they are persistent. Johnson & Johnson is planning its own pediatric studies.
First author on the paper, Dr Helen Parry, a National Institute for Health Research academic clinical lecturer at the University of Birmingham, said: "Our research provides further evidence that the mRNA vaccine platform delivers a strong immune antibody response in people up to 96 years of age and retains broad efficacy against the P.1 (Brazilian) variant, which is a variant of concern".