Three doses of Pfizer jab are required to provide full protection against Omicron variant, pharma giant admits after study said two doses of vaccine provide 41 times less virus fighting antibodies
Pfizer's Covid booster vaccine triggers a 25-fold spike in antibody levels against Omicron, the drug firm claimed today but it admitted two doses may not be enough to thwart the mutant strain.
The vaccine manufacturer argued three injections provide a 'more robust' defence against the variant, which has sown chaos since it was first identified in South Africa last month.
A third jab triggers a similar antibody response against Omicron as two doses against previous strains of Covid, according to preliminary laboratory tests. It also 'strongly increases' T cell levels, offering the immune system an extra boost to protect against severe disease.
But Pfizer also insisted that two doses should still be enough to slash rates of hospitalisations and deaths, in the event of fresh waves triggered by the super-mutant strain.
It comes as two separate studies released today show that vaccines appear to work better than expected against Omicron, which is quickly spreading in Britain and has left No10 on the brink of resorting to its 'Plan B' to save the NHS from being overwhelmed this winter.
A South African research institute found people fully-vaccinated with Pfizer make up to 40-times fewer antibodies against Omicron compared to other variants. But the lead author of the research, the first of four laboratory-based studies released in the last 24 hours, insisted the results are 'better than expected'.
Another study by Swedish virologists also found there is a drop in the body's ability to neutralise Omicron after jabs. But the Karolinska Institute researchers insisted the decline was not seen in everyone, with one of the paper authors saying the fall was 'lower than feared'.
Meanwhile, a World Health Organization official insisted the vaccines should still work against Omicron, admitting that the strain appears to be milder than its rivals, such as Beta and Delta.
Dr Michael Ryan, the agency's emergencies director, argued the current jabs 'have proved effective against all the variants so far' in preventing severe disease. He added that 'there's no reason to expect' vaccines would suddenly fail against Omicron.
But top Government advisers have warned that the NHS could still face severe pressure this winter from Omicron if it is definitively proven to be more transmissible, simply because of the sheer number of people who would get infected. Vaccines are extremely effective but not perfect at protecting against severe outcomes.
However, a fourth laboratory study — based on testing blood from fully-vaccinated people — suggested the variant could evade protection from booster jabs. Medics at University Hospital Frankfurt, who carried out the study, said there were 37 times fewer antibodies made against Omicron compared to Delta.
Despite all four studies showing a drop in antibodies against Omicron, it is unclear how much this will effect the efficacy rates, especially against serious illness, hospitalisations and deaths. Other parts of the immune system, such as T cells, are considered key in fighting off the virus.
UK officials hope the country's booster roll-out to all adults — which Boris Johnson pledged to deliver by the end of January — will save the NHS in the face of the oncoming wave of Omicron, which leading scientists believe will be dominant by Christmas.
Researchers at the African Health Research Institute (AHRI) found the Pfizer vaccine triggers forty times fewer antibodies capable of fighting the Omicron variant compared to an older version of the virus. The graph shows that antibody levels — scientifically known as geometric mean titer (GMT) FRNT50 — among 12 people jumped to an average of 1,321 when they were exposed to an older strain of the virus (D614G). But when scientists tested their blood against Omicron, antibody levels dropped to an average of 32, marking a 41.4-fold decrease. Six of the volunteers were double-jabbed with Pfizer (orange), while the other half were double-jabbed with Pfizer and had previously tested positive for Covid. People previously infected with Covid had the most protection
A separate study by researchers at the Karolinska Institute in Stockholm, Sweden found that while there is a drop in the body's ability to neutralise Omicron it is not seen in everyone and is a smaller drop than feared. Their findings are based on recent blood samples from 17 people in Stockholm (shown in middle graph), compared to 17 hospital workers who were previously infected with the original Wuhan strain (shown in right graph). The middle and right graphs show the participants antibody levels when exposed to the Wuhan variant (WT) compared to Omicron. The left graph shows the average antibody levels recorded among both groups when exposed to the original strain (purple), Delta (blue) and Omicron (green)
Eminent epidemiologist Professor Tim Spector claimed infections of the highly evolved variant were doubling every two days. The above graph, based on MailOnline analysis, shows how the number of daily cases of Omicron could breach the 100,000 barrier before New Year's Day, if that pace continues
No10 announced last week that it plans to ramp up the booster programme to 500,000 jabs per day and offer a third dose to all 53million British adults by the end of January to shield against the incoming wave. But the scheme already appears to be stalling with less than 330,000 delivered across Britain yesterday and just 380,000 administered each day on average. At the current rate, all eligible adults will not be boosted until February 10
Pfizer's results are based on a laboratory study using the blood of 20 people, who were either double-jabbed three weeks earlier or triple-jabbed one month earlier with its vaccine, which Britain is using for its booster programme.
The results showed the third dose may provide a 'more robust protection', triggering a 25-fold jump in antibody levels.
Pfizer, which manufactured the jab with German partner firm BioNTech, said the levels equated to a 'high efficacy' based on data against other variants.
A booster jab offered a boost in antibody levels that are 'comparable to those observed' for the original Wuhan virus after two doses, the company said.
The level of neutralising antibodies against Omicron after three jabs was 154, compared to 155 against the Wuhan strain after two jabs.
But the figure was 60 per cent lower than levels seen for three doses against Delta.
Experts today cautioned that a drop in antibody levels doesn't necessarily translate into vaccine efficacy, but merely gives an indicator as to what can be expected.
Announcing its results today, Pfizer also said booster injections appeared to increase a specific kind of T cell, which is thought to play a crucial role in staving off severe illness.
Antibodies attack the virus and stop it attaching to and infecting the body's cells.
If the virus manages to breach that defence, T cell protection identifies them and stops them spreading further.
The company — which has earned billions through the pandemic after making an effective jab — will collect data on whether the antibodies remain at that level in the months after a booster dose, with immunity known to wane slightly over time.
It will also monitor real-world data to better understand how its jabs perform against the strain.
Meanwhile, blood samples among double-jabbed people showed a 25-fold reduction in antibody levels against Omicron, compared to the original strain.
Three weeks after the second dose, antibody levels stood at 155 against the Wuhan stain, while it dropped to 6 against Omicron.
A sharp reduction was also seen against the Beta variant, which triggered six times less antibodies (36) than the original strain.
He said the Omicron variant 'came as a surprise' because it has three times as many mutations as experts were used to seeing on variants.
Dr Bourla said: 'Although two doses of the vaccine may still offer protection against severe disease caused by the Omicron strain, it's clear from these preliminary data that protection is improved with a third dose of our vaccine.
'Ensuring as many people as possible are fully vaccinated with the first two dose series and a booster remains the best course of action to prevent the spread of Covid.'
Ugur Sahin, chief executive officer and co-founder of BioNTech, said: 'Broad vaccination and booster campaigns around the world could help us to better protect people everywhere and to get through the winter season.
'We continue to work on an adapted vaccine which, we believe, will help to induce a high level of protection against Omicron-induced Covid disease as well as a prolonged protection compared to the current vaccine.'
Pfizer began developing a Covid vaccine to specifically targets the Omicron variant on November 25, which it can dish out from March 2022 if the current crop of jabs are not providing sufficient protection.
Earlier versions of the new vaccine will be ready for pre-clinical trials in January.
Some 437 Omicron cases have been spotted in the UK since the virus was first identified in South Africa.
The Government has reintroduced mandatory face covering rules, added 11 countries to the red list and imposed tighter restrictions for UK arrivals in a bid to control the spread of the variant.
WHO official Dr Ryan today said the strain is likely more transmissible than previous variants but is 'highly unlikely' to completely evade vaccines.
He said: 'The preliminary data doesn't indicate that this is more severe. In fact, if anything, the direction is towards less severity.'
However, Dr Ryan acknowledged that it was possible that existing vaccines may prove less effective against Omicron, which counts more than 30 mutations on the spike protein that dots the surface of the coronavirus and allows it to invade cells.
It comes after researchers at the African Health Research Institute (AHRI) claimed people who received the Pfizer vaccine make 40-times fewer antibodies that can defend against Omicron.
The scientists examined blood samples from 12 people double-jabbed from Pfizer who had not yet received their booster.
The pre-print study, which is yet to be peer-reviewed, found Omicron could seemingly dodge many vaccine-triggered antibodies.
However, the study only looked at antibodies, which are just one part of the immune response that fights off the virus. Although they are normally a reliable indicator of immunity.
It is not clear whether the reduced number of antibodies will translate into lower protection against severe illness, hospitalisation and death among those who catch the strain.
Professor Alex Sigal, a virologist at the AHRI who led the study, tweeted that the results of the study are 'better than I expected of Omicron'.
He noted there is a 'very large drop' in protection from Pfizer compared to other variants, but those who previously had Covid and are vaccinated were more protected against the variant.
Professor Daniel Altmann, an immunologist at Imperial College London, said the study offers a 'clear message' that those who are unvaccinated or double-jabbed 'are likely to be highly vulnerable to infection'.
'However, those who've seen spike three times, either by boosting or by infection plus two doses, appear generally in the safety zone, even with a 41-fold drop,' he said.
The study provides 'an even stronger argument for getting boosters as widely and rapidly as possible', Professor Altmann said.
And Professor Penny Ward, an expert in pharmaceutical medicine at King's College London, said it is 'not surprising' that higher levels of antibodies are needed to neutralise Omicron compared to other strains due to its 'complex series of mutations'.
She noted that when scientists looked at other strains in the laboratory they found similar reductions in vaccine effectiveness, but this did not lead to a real-world drop in protection against severe illness.
Dr Michael Ryan, the WHO's emergencies director said: 'The preliminary data doesn't indicate that this is more severe. In fact, if anything, the direction is towards less severity'
'After a year's experience with the Covid vaccines, we know that lower levels of antibody, while being less effective at preventing infection, remain very highly effective at reducing hospitalisation and mortality rates,' Professor Ward added.
And Professor Jonathan Ball, a virologist at the University of Nottingham, noted that while 'the amount of virus killing observed in the lab is reduced markedly – up to 40-times reduction – there is still measurable virus neutralisation, especially in those who were vaccinated and previously infected.'
'This group effectively mimics what we would expect in people who had had two doses of vaccine plus a boost,' he said.
Professor Ball added: 'Whilst we do not fully understand what protective immunity looks like, the data should give us reassurance that the vaccine will still offer protection.
'The other thing to remember is that many of the vaccines also generate T cell immunity and we think that this will be less impacted by the high level of mutations that omicron has.
'Whilst this reduced antibody immunity might mean more people can be infected and have mild symptoms, I am still confident that the vaccines, especially after a boost, will still protect from serious disease.
'That's why we still need to get the message across, get vaccinated, get boosted, even if you have been infected before.'
And a separate study by researchers in Sweden found that while there is a drop in the body's ability to neutralise Omicron is not seen in everyone and is a smaller drop than feared.
Scientists at the Karolinska Institute in Stockholm found there was an average seven-fold drop in neutralisation potency among 17 blood donors.
Benjamin Murrell, an assistant professor in computational biology, virology and immunology and one of the researchers behind the study, said this is 'certainly worse than Delta' but is not 'as extreme as we expected'.
He said Professor Sigal's study reported a 'much more substantial average reduction' but noted 'what is common is that neutralisation is not completely lost for all samples, which is positive'.
A third set of results shared by researchers in Germany found neutralising antibodies from two doses of the vaccines used in the UK are ineffective against the strain.
Dr Sandra Ciesek, a virologist at the German Center for Infection Research, tweeted laboratory findings, which have not yet been published, show that six months after two doses of Pfizer or Moderna, or a first dose of AstraZeneca and second dose of Pfizer, there was no neutralising antibodies present that could protect against Omicron.
And even three months after being boosted with the Pfizer jab, people had just 25 per cent protection from neutralising antibodies against Omicron, compared to 95 per cent protection at the same point against Delta.
Dr Ciesek said this translates into a 37-fold reduction against Omicron compared to the Delta strain.
The findings confirm that developing new vaccines that target Omicron 'makes sense', she said.
But Dr Ciesek noted that the results 'cannot say anything' about whether people are still protected from severe illness, which other parts of the immune system play a key part in warding off.
Professor Francois Balloux, a geneticist at University College London, said results from the different neutralisation studies are difficult to compare and it is too early to know why the results from the German study 'look so much worse'.
'Whatever the reason, those results do not suggest that neutralising antibody activity can be restored by a third dose,' he said.
This is the image that has sparked fear among scientists, prompted ministers to turbocharge the UK's booster vaccine rollout and seen the return of mask mandates in England. It details the new super-mutant Omicron variant's spike protein mutations which experts fear will make it the most infectious and vaccine-resistant strain yet. The graphic, released by the country's top variant monitoring team, also lays bare how it is far more evolved than even the world-dominant Delta strain, with nearly five times as many alterations on the spike
'Those results suggests that a large proportion of the population globally is at risk of (re-)infection by the omicron variant over the coming months,' Professor Balloux said.
But he noted milder symptoms have so far been recorded among those infected with Omicron.
And real-world data suggests vaccines are still protecting against severe illness through other antibodies and T cells, Professor Balloux added.
Top US scientist Anthony Fauci echoed the WHO's view, saying Omicron did not appear worse than prior strains based on early indications - and was possibly milder.
The new variant is 'clearly highly transmissible,' very likely more so than Delta, the current dominant global strain, Fauci told AFP.
'It almost certainly is not more severe than Delta,' he added. 'There is some suggestion that it might even be less severe.'
But he noted it was important to not over-interpret this data because the populations being followed skewed young and were less likely to become hospitalised. Severe disease can also take weeks to develop.
'Then as we get more infections throughout the rest of the world, it might take longer to see what's the level of severity.'
It comes as UK daily Covid infections jumped 15 per cent in a week to 45,691, with scientists estimating Omicron cases are doubling every two days.
'Professor Lockdown' Neil Ferguson today admitted that another nationwide shutdown could be on the cards to tackle Omicron.
The Government scientist, whose modelling bounced No10 into the original lockdown last spring, said the return of stay-at-home orders 'certainly might be possible' if the mutant strain threatens to overwhelm the NHS.
He told the BBC Radio 4 Today programme: 'There is a rationale, just epidemiologically, to try and slow this down, to buy us more time principally to get boosters into people's arms because we do think people who are boosted will have the best level of protection possible, but also to buy us more time to really better characterise the threat.'
Asked outright if a lockdown could be reimposed, he said: 'Clearly if the consensus is it's highly likely that the NHS is overwhelmed then it will be for the Government to decide what to do about that but it's a difficult situation to be in of course. It certainly might be possible at the current time.'
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