Pfizer's Covid-19 vaccine successfully provokes immune response in early clinical study raising hope for the jab already ordered by UK officials

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A Covid-19 vaccine made by the pharmaceutical company Pfizer has passed safety and effectiveness tests in early clinical trials, a study revealed today.

The jab, of which the UK Government has ordered 30million doses, is now another promising candidate for the vaccine considered so crucial to stopping the virus.

Early human trials of the injection, carried out by New York-based Pfizer and universities and hospitals in the US, have produced promising results.

People who received the vaccine produced immune responses on par with - or better than - those who had actually had coronavirus in the past.

And no dangerous side effects were reported among the 36 adults who received the jab in the tests, who most commonly complained of headache and tiredness. 

Pfizer's attempt to make a vaccine, which it has called BNT162b1, is the latest in a line of hopeful trial results, with Britain's own vaccines made by Oxford University and Imperial College London also showing early signs of success in human testing.

Russia's Government yesterday became the first in the world to officially register a vaccine but scientists were sceptical because the jab had been tested on fewer than 40 people and no data is publicly available to see if it works or is safe.

New York-based Pfizer, in conjunction with hospitals and universities in the US, tested its jab on 36 volunteers and found an immune response on par with people who had actually had coronavirus

The results of a first phase trial of Pfizer's vaccine were published in the prestigious science journal Nature today.

Researchers, who included Pfizer staff, said the vaccine had successfully produced an immune response in the bodies of the people it was given to.

The purpose of the jab is to trick the immune system into thinking it is infected with the coronavirus, effectively training it how to fight it off without someone actually being sick.

Forty-five adults aged 18 to 55 were involved in the trial and given a jab of 10 micrograms, 30 micrograms or 100 micrograms, or a placebo.

Researchers found the immune response was much stronger in the 30 microgram group than in the 10.

However, there were no notable differences in immune response between the 30 and 100 groups after one dose - and the 100 micogram group suffered more side effects.

In the trial the scientists reported that the levels of antibodies - substances used by the immune system to fight illness - in the participants was on par with people who had actually fought off the real coronavirus, or up to four times higher in some.

While the former patients' blood contained an average of 602 units per millilitre after two weeks, vaccine recipients had between 534 and 1,778 U/mL after three weeks.

Although immunity to Covid-19 is still unclear, having more antibodies generally means someone is better equipped to fend off the illness. 

The researchers wrote: 'Robust immunogenicity was observed after vaccination with BNT162b1.'

They added: 'The clinical findings for the BNT162b1 RNA-based vaccine candidate are encouraging and strongly support accelerated clinical development, including efficacy testing, and at-risk manufacturing to maximise the opportunity for the rapid production of a Sars-CoV-2 vaccine to prevent Covid-19.'

Pfizer's jab is a type of vaccine called a lipid nanoparticle vaccine, meaning genetic material linked to the coronavirus is transported into the body inside a bubble made of lipids, which are fatty molecules.

These are synthetic which makes them easy to produce en masse, whereas other types of vaccine can use different viruses or parts of the coronavirus itself to transport the genetic material (RNA).

Once the RNA is inside the body it triggers the immune system to react in the same way that it would if someone was genuinely infected with Covid-19.

This can sometimes cause side effects - discovering these is one of the main purposes of clinical trials.

The Pfizer trial found that most of the 36 people who received the jab suffered from pain at the injection site, and it was less common in the nine people who received a placebo.

Some people who received the jab also suffered from 'mild to moderate fatigue' and headaches in the week after the jab. Some also had chills muscle pain and joint pain which people in the placebo group didn't have.  

The paper comes after Russia yesterday revealed that its authorities have approved a vaccine being made in the country, and that President Vladimir Putin's own daughter has taken it.

But scientists are sceptical and said the jab has only been tried on around 40 people and that there is no public data to suggest it works. 

Russia has made the vaccine race a matter of national prestige and named the product 'Sputnik V' after the former Soviet space satellites, prompting fears that safety will be compromised for the sake of Russia's image.     

Scientists yesterday criticised Putin for the 'reckless and foolish' move which they say could make the pandemic worse if the vaccine proves dangerous or ineffective.  

While Putin said his daughter had suffered no side effects worse than a high temperature, news agency Fontanka claimed there were a long list of 'adverse events' (AEs) which occurred 'frequently and very often'.   

'It is not possible to more accurately determine the incidence of AEs due to the limited sample of study participants,' said the Gamaleya Research Institute which produced the vaccine.

The vaccine was approved after just 42 days of testing on 38 people, it reported.