Pfizer and its German partner BioNTech released a second batch of interim results on Wednesday, saying their two-dose coronavirus vaccine candidate is 95 per cent effective and also protects the most vulnerable people in older age groups from the risk of falling prey to the virus.

The company said that no serious side effects have shown up. The most common complaint was fatigue after the second vaccine dose, affecting about 4 per cent of the participants who got the shot.

Pfizer and BioNTech plan to apply "within days" to US regulators for emergency use approval.

The Pfizer news comes at a critical time in the global race for a cure for the virus, especially in the US which has the world's highest coronavirus caseload and is facing a nightmarish winter surge across 50 states. More than 11 million Americans have contracted the virus while over 248,000 have died from it.

The Pfizer vaccine comes loaded with one tricky logistical challenge: It needs to be stored at extreme sub-zero temperatures. Moderna - the other US pharma giant which has released 94.5 per cent efficacy results - says its vaccine remains stable at home refrigerator temperatures for 30 days.

Pfizer and BioNTech expect to produce a total of 50 million vaccine doses in 2020 and up to 1.3 billion doses in 2021. US regulators hope to have 20 million vaccine doses each from Moderna and Pfizer available for distribution in late December. The first wave of vaccination will be for those in the most vulnerable groups. Non-high risk populations will have to wait until Spring or more likely the Summer of 2021 to get a shot.

"Primary efficacy analysis demonstrates BNT162b2 to be 95 pert cent effective against Covid-19 beginning 28 days after the first dose; 170 confirmed cases of Covid-19 were evaluated, with 162 observed in the placebo group versus 8 in the vaccine group," Pfizer said on Wednesday.

The latest announcement comes a little over a week after Pfizer's first bombshell announcement on November 9 that its vaccine is 90 per cent effective. In the first round, Pfizer based its results on a total of 94 infections.

Pfizer-BioNTech use the 'mRNA' technology which means the vaccine is not embedded with the virus itself and there is therefore no risk of catching Covid-19 from the shot itself. The vaccine is infused with a piece of genetic code that trains our immune system to recognise the spike in protein on the surface of the virus - a lethal signature of the coronavirus.

The Pfizer study has enrolled nearly 44,000 people for its study and will continue to collect data for two more years.