Researchers found in a small study that recipients of the jab developed up to 20 times more antibodies within a week of having the second dose of the jab.
Higher levels of antibodies likely lead to a stronger immune response which could clear the virus before someone has a chance to spread it, but this is still not proven.
Until now, scientists didn’t know whether vaccines would stop transmission and were banking only on it preventing severe illness and death. Pfizer itself has not published any data showing how the jab affects the spread of the disease.
Developers of other vaccines have also not offered any proof that their vaccines will be able to reduce transmission of the virus.
The survey done on 102 hospital staff in Israel is the first indication that a Covid-19 vaccine may stop transmission. It saw all but two of them develop antibody levels that were even higher than patients who had recovered from Covid-19.
Antibodies are substances produced by the immune system which store memories of how to fight off a specific virus.
Study leader Professor Gili Regev-Yochay said the results were ‘encouraging and reasonable to assume that these people will not be carriers or contagious, although that is still not a direct conclusion,’ the International Business Times reported.
Recipients of the Pfizer/Biotech vaccine developed up to 20 times more antibodies within a week of having the second dose of the jab. Pictured: A key worker receives the Pfizer-BioNTech jab at the Life Science Centre, Newcastle upon Tyne
Medics running the study found that 100 out of 102 people mounted large antibody responses to the coronavirus after two doses of the vaccine.
The research was done on members of staff at the Sheba Medical Centre in Tel Aviv.
One of the two who didn’t had a compromised immune system; the other is still being investigated, The Telegraph reports.
HOW COULD A VACCINE STOP THE VIRUS SPREADING?
The main purpose of the Covid-19 vaccines when they were developed was to give people some early immunity against the virus so they wouldn’t end up in hospital or die if they caught it.
The jabs developed so far have all shown signs of being able to do this and are being rolled out to try and stem the tide of deaths caused by Covid.
But if the vaccines produce a strong enough immune response they could also stop the virus from spreading by training people’s bodies to destroy it on sight.
Immunity developed by vaccines is based on substances called antibodies and also other types of immune substances such as white blood cells.
These destroy the virus when it gets into the body, stopping it from reproducing and entering the body to cause infection.
Any amount of this protection will likely reduce the risk of illness and death because it reduces how much of the virus can get into the body, but a weak response might allow the virus to linger in the body for a short period of time, during which people might be infectious to others even if they don’t get ill themselves.
A strong immune response from a highly effective vaccine, however, could make the body so good at destroying the virus that all of it gets eliminated as soon as it enters the body of a vaccinated person.
This could mean it exists for too short a period of time for the person to breathe it out and spread it to other people.
None of the vaccine-makers have yet published data showing whether this will be the case.
Antibodies are critical for the immune system because they both destroy viruses and also flag them up for destruction by other white blood cells.
The director of the hospital’s Infectious Disease Epidemiology Unit, Professor Regev-Yochay, said she thought it was unlikely that people who receive two doses of jab would spread the illness.
This is expected to be because they develop strong enough immunity that the virus cannot reproduce in their body.
It is possible that if people have vaccines that aren’t highly effective, the virus can continue to circulate in their body for a short while without making them ill but still allowing them to pass it on.
Professor Regev-Yochay said in a briefing yesterday: ‘The results of the survey are in line with Pfizer’s experiment and even better than expected,’ the Jerusalem Post reported.
‘I expect that the survey results of the other employees participating will be similar. There is certainly reason for optimism.’
Israel has had one of the world’s fastest Covid vaccination programme and has given jabs to 2.6million of its 9million people already.
But the country has yet to see its infection and death numbers come tumbling down after four weeks of immunisations.
Studies from the country suggest the jab could eventually slow the rate of contagion by up to 50 per cent as well as stopping infected recipients becoming sick.
While Israel is leading the world in the vaccine race with more than one in five people receiving an initial dose, its infection rates were last week at their highest ever with more than 8,000 positive tests per day and a record 1,102 patients in hospital.
The vaccine trials run by Pfizer, Moderna, Johnson & Johnson and Oxford University and AstraZeneca had one primary goal which was to try and reduce Covid-19 rates.
To do that, the scientists simply vaccinated half of their volunteers with two doses apiece, and gave the other half two doses of a placebo jab.
They then recorded how many people were diagnosed with Covid-19 after the vaccine, they did not test how much participants caught or transmitted the virus without knowing.
In earlier tests in monkeys, animals that got Pfizer’s jab had no traces of the virus in their respiratory tracts, and earlier tests in people showed they produced plenty of antibodies after vaccination.
The global trials run by Pfizer (pictured, Pfizer-BioNTech vaccine), Moderna, Johnson & Johnson and Oxford University and AstraZeneca had one primary goal
On Tuesday, Israel saw daily Covid-19 infections and active cases reach all time-highs. On Tuesday, Israel reported 9,997 new cases – its highest in a single 24 hours – and 46 deaths, after recording a record 67 deaths on Monday
Combined with the final clinical trial data, that suggests that the vaccine is triggering an immune response, and that immune response is strong enough to keep the virus from copying itself and spreading in the body.
In turn, that means the odds are low that someone’s viral load – the concentration of virus in their cells – is high enough to spread the infection.
However the trials that Pfizer completed were not designed to state for sure that the vaccine can slow the spread of the virus.
It comes after nearly 5million people aged between 70 and 80 are being invited to receive their first dose, with some in Whitehall suggesting the rollout is going so well that the wider adult population could be covered by June rather than September.
However, vaccines minister Nadhim Zahawi said people in their 70s will only be offered jabs in areas where the ‘majority’ of over-80s have already had their first shot.
That could mean people in areas such as London and Suffolk, where progress has been slower, will have to wait longer.
WHAT ARE THE KNOWN SIDE EFFECTS OF THE PFIZER VACCINE?
The UK medicines regulator advised today that anyone who has a history of ‘significant’ allergic reactions to medicines, food or vaccines should not get the Pfizer coronavirus jab.
Dr June Raine, the chief executive of the MHRA, told Parliament’s Science and Technology Committee that this was not identified in the trials.
‘We know from very extensive clinical trials that this wasn’t a feature,’ she said.
Allergic reactions to the vaccine are ‘very rare’, according to the trials involving more than 40,000 people.
Pfizer found a ‘very small number’ during its phase three clinical studies, which found 137 out of 19,000 people. This compared to a comparable 111 in a group of the same size who didn’t get the vaccine.
They also identified 12 possible side-effects from the vaccine, with seven identified as ‘very common’ meaning they are likely to affect more than one in ten people. Below are the known side effects.
The patient safety leaflet for the vaccine cautions that anyone with an allergy to any of the active substances in the vaccine should not receive the jab.
It adds: ‘Signs of an allergic reaction may include itchy skin rash, shortness of breath and swelling of the face or tongue.’
Allergic reactions to the vaccine are:
Very common (Likely to affect more than one in ten people)
- Pain at injection site
- Muscle pain
- Joint pain
Common (Likely to affect up to one in ten people)
- Injection site swelling
- Redness at injection site
Uncommon (May affect one in 100 people)
- Enlarged lymph nodes
- Feeling unwell