select search filters
roundups & rapid reactions
before the headlines
Fiona fox's blog

expert reaction to modelling of booster effectiveness against omicron by Imperial College London

Modelling by Imperial College London looks at booster vaccine effectiveness against the Omicron variant of SARS-CoV-2.

This Roundup accompanied an SMC Briefing.


Prof James Naismith, Director of the Rosalind Franklin Institute, and Professor of Structural Biology, University of Oxford, said:

“The paper confirms and expands our knowledge about Omicron. The vaccines in use in the UK target Spike protein. The most potent antibodies bind to the ACE2 epitope on Spike.

“The vaccines were developed against a different strain of the virus, thus Omicron cannot be targeted by many of the most potent antibodies.

“As a result, neutralisation of Omicron in vaccinated people relies on the second team of antibodies. The effect is weaker but can be compensated by have more of them.

“The booster produces more antibodies of all sorts against the Spike and therefore is effective at neutralising the virus and preventing infection. As the data show, boosters will be effective at reducing infection.

“The amount of antibodies drops with time, something we have known with Delta. What the paper shows is that this might be more rapid with Omicron with drop off in a couple of months.

“The issue being addressed here is infection and spread. 

“Serious disease is a different question, we can be confident that double and especially triple vaccinated have protection against serious disease.

“As a result the number of hospitalisations per 1000 infections of Omicron will be significantly lower than the first wave. Better medicines and treatments will help too. 

“A partial solution to the waning of immunity would be reformulate the vaccine to the Omicron strain. There is a logic to this, but there are important considerations.

(1) Delta may continue to circulate, the most potent anti Omicron antibodies may not be very good against Delta.

(2) Boosting with the current vaccines may provide enough T-cell immunity to prevent serious disease and coupled to new medicines coming along may be enough in the future.

(3) Shutting down and restarting is very disruptive. Any delay in vaccination will cost lives; careful analysis of cost benefit ratios are needed.

(4) Vaccinating the unvaccinated should not be delayed.

“I take the opportunity to comment on the attacks on Professor Whitty. In our democracy, decisions about what laws we must follow are taken in Parliament

“Quite rightly the responsibility belongs to politicians for the outcomes of those decisions in terms of deaths and disease.

“The Chief Medical Officer is by an act of Parliament required to give an independent (non-political) assessment of public health.

“Professor Whitty is highly regarded medical scientist whose opinions are based on sound evidence and have saved lives.

“Professor Whitty has never voted in the House of Commons or Lords, he has passed no laws.

“I am not in favour of turning the CMO into a party political position; the current model has served us well in my view.

“If Parliament decides it no longer wishes to have an independent CMO but rather wants to appoint a political (government) spokesperson, then the power to do this is in Parliament, simply pass the law.

“Personal attacks on Professor Whitty for carrying out the duties assigned to him by law are wrong.”


Dr Clive Dix, former Chair of the UK Vaccine Taskforce, said:

“It is important not to over interpret this data. The conclusions made are based on making assumptions about omicron where we still don’t have sufficient data.

“For example, we have no data on the cellular immune response which is now probably driving effectiveness of vaccines. This is a crucial missing assumption in the modelling.

“Some of their conclusions are different to the data emerging from South Africa in that the vaccines are holding up well against severe disease and death at present.

“There is a huge amount of uncertainty in these modelled estimates and we can only be confident about the impact of boosters against omicron when we have another month of real world data on hospitalisation, ICU numbers and deaths. 

“It remains the case that we still need to get vaccines current and future to the whole world.”


Prof Penny Ward, Independent Pharmaceutical Physician, and Visiting Professor in Pharmaceutical Medicine at King’s College London, said:

“The modelling group from Imperial College have been busy today releasing two papers of interest, this being the first. The study is a modelling exercise incorporating the impact of neutralising antibody titres and rate of change vs incidence of disease, hospitalisations and deaths post time from completion of the primary course and booster vaccination associated with the omicron wave when compared to the preceding delta wave. The model, not surprisingly, suggests a decline in protection against symptomatic infection caused by the omicron variant with this translating into a slightly increased risk of more severe disease 2 months post booster when compared to data for disease caused by the delta variant. Critical assumptions in this model include the proportionate increase in neutralising antibody titre associated with boosting and the rate of decline of these antibodies over time post boost. In all scenarios, the healthcare burden associated with infection caused by this variant is substantial suggesting that immunisation with a matched vaccine may be important, alongside reintroduction of non pharmaceutical interventions to prevent social mixing and control disease spread in most countries, regardless of prior history of infection. In the event of restricted vaccine availability, targeting the most vulnerable population groups is more effective at protecting healthcare services than targeting young fit adults. It remains to be seen which of these modelled scenarios more closely mimics actual outcomes: with the current rate of infection we may have a better understanding of this in mid to late January 2022. The data reiterate the inherent weakness of a ‘vaccine only’ strategy to disease control with a rapidly mutating viral illness. It would be helpful to start incorporating the impact of additional antiviral approaches into these models now that antiviral agents are becoming available, to further assess the added benefit these agents may provide to maintaining societal well being rather than resorting to repeated lock downs, with all that implies for the economic health of nations, indefinitely.”



‘Report 48 – The value of vaccine booster doses to mitigate the global impact of the Omicron SARS-CoV-2 variant’ by Azra Ghani et al. This work is not peer reviewed.  



All our previous output on this subject can be seen at this weblink:



Declared interests

Prof Penny Ward: “I am semi-retired, but I am owner/Director of PWG Consulting (Biopharma) Ltd a consulting firm advising companies on drug and device development. Between December 2016 and July 2019 I served as Chief Medical Officer of Virion Biotherapeutics Ltd, a company developing antiviral treatments for respiratory viral diseases. Previous employee of Roche, makers of tocilizumab (anti IL6 antibody) and CMO of Novimmune, makers of empalumab (anti IFN gamma antibody).”

None others received.




in this section

filter RoundUps by year

search by tag