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expert reaction to new JCVI advice on COVID-19 booster vaccines for those aged 18 to 39 and a second dose for ages 12 to 15

The Joint Committee on Vaccination and Immunisation (JCVI) have released their updated advice on COVID-19 booster vaccines for those aged 18 to 39 and a second dose for those aged 12 to 15.


Prof Adam Finn, Professor of Paediatrics, University of Bristol, said:

“The twin concepts driving today’s JCVI recommendations are firstly that it should be possible to compensate to some degree for any significant antigenic drift in omicron by increasing neutralising antibody titres with booster doses and secondly that any such measures can only have any valuable impact if they are implemented early, before any large omicron wave – if there is one – becomes established. This is because both delivery of vaccines and generation of immune responses once administered take time.

“Meantime efforts to reduce transmission through contact tracing, isolation, mask wearing and travel restrictions and thus to delay and diminish any such wave will help buy time to put these measures into effect.

“While it is better to wait for plenty of solid evidence to drive policy whenever you can, we currently face a situation where doing that could substantially increase additional risk and could render any actions ineffective through delay.

“Moving forward, the biggest immediate challenge will be to translate these simple-sounding policy changes into operation in a structured and logical and fast-moving way. Doing so will be very difficult as the programme becomes ever more complex both to deliver and to communicate.

“Regarding second doses for children aged 12-15 years, a decision on this was always expected around now and depended primarily on very reassuring data from MHRA around safety, rather than the emergence of omicron. Some other countries have seen higher safety signals following second doses especially in males, whereas this is not evident in the UK figures to date, possibly because of the longer doses interval we use. Nevertheless the higher antibody responses to be expected after the second dose have the potential to help reduce infection rates in this age group too, in the way discussed above, if a significant omicron wave materialises.”


Prof Deborah Dunn-Walters, Professor of Immunology, University of Surrey & Chair of the British Society for Immunology COVID-19 and Immunology taskforce, said:

“It is important to realise that definitive evidence with respect to Omicron variant is not yet available, although scientists are working quickly to find answers to the important questions:  Is this variant more infectious?  Does it cause a worse disease? Can it escape our immunity?

“In the absence of hard evidence, we rely on making assumptions based on the evidence we have so far, and the knowledge we have of how the immune system works.  Early indications are that the Omicron variant may be more infectious and rapidly taking over from the Delta variant.  This is based in part on the rapid increase in cases that fail one part of the PCR test, that part that detects “S gene”.  The Omicron variant has very high numbers of mutations in the S gene.  Further sequencing will provide more clarity in time. 

“S gene mutations will change the S protein, the same protein that is used in the vaccine.  A theoretical prediction is that antibodies to existing vaccines and variants will therefore not be able to bind to Omicron S protein as well as to the original virus.  However, we would predict that there will still be some protective immunity because our immunity is extremely diverse – lots of different kinds of antibodies will bind in many different places and not all will be changed in Omicron. There will also be T cells that can still recognise parts of the protein.  Work is ongoing to look at levels of immune response to Omicron.

“Until the answers to these questions are known it is sensible to increase protective measures where we can.  Since we know that immunity does wane to some extent, and that boosters can increase immunity, then accelerating the booster program will protect more people.  It would not be useful to have a third dose of vaccine too early after the first two. We know that immune responses are boosted more effectively if the immune system has a time to process the previous challenges first.  Hence it has not been recommended to boost with the third dose before 3 months has elapsed since the second jab. But bringing the date forward from the 6 month interval and opening boosters to all adults will protect a large number of people.  I would urge anyone that has not yet had their first doses of vaccine to consider getting them.  Protection against serious disease is very high after vaccination and I do not anticipate this protection would be significantly lost with the new variant. Vaccines can also boost the protection that you may have gained from having had COVID-19.”


Comments sent out earlier on Monday in response to news reports suggesting what the JCVI would say, before the detail was announced:

Prof Penny Ward, Independent Pharmaceutical Physician, Visiting Professor in Pharmaceutical Medicine at Kings College, London, said:

“The rapid identification of a new strain which contains multiple genetic mutations and the further rapid action taken to try to constrain spread while further data are gathered is a welcome change from previous behaviour.

“Based on the clinical information from SA the pattern of disease is broadly similar to the delta strain, however as the average age of patients in SA is younger than in the UK population, and we know that, with all previous waves of infection cause by new strains, older frailer patients experience more severe disease appropriate caution is needed to try to prevent uncontrolled community spread.

“Urgent work is clearly underway to evaluate the clinical pattern of disease caused by this strain and also the extent to which this virus is susceptible to vaccination induced immunity, but even while we wait for these results, accelerating the booster campaign and urging more eligible people that have yet to be vaccinated to come forward for vaccination is sensible. The vaccines in use provide a measure of broad immunity against viral variants and also induce cellular immunity which can also confer broader coverage of new emergent strains and protection from more serious disease if infected. If, as might be logically suspected, vaccine protection starts to diminish after 120 days in people under the age of 40 extending the age range for booster shots and potentially shortening the interval between the second and third shot would also be appropriate. Younger teenage and children over 5 may be expected to respond rapidly to vaccination and this too may both protect them from infection and illness, with its attendant impact on schooling, and further reduce potential for community spread. MHRA have not yet approved any vaccine for use in children under 12 in the UK, but as EMA has approved the Pfizer-BioNTech vaccine for use in this age group which suggests that extending the age range for vaccination to younger children would be medically reasonable.

“In the meantime, this variant strain can be expected to be susceptible to molnupiravir and to Paxlovid, enabling alternative approaches for treatment/local outbreak control using these antiviral medications in those at highest risk of severe outcomes – this was anticipated to be evaluated in a large community study, PANORAMIC, which will open for recruitment shortly. This strain’s susceptibility to the various monoclonal antibodies including Ronapreve also needs to be evaluated. Ronapreve is currently the only treatment option in clinical use in hospitalised patients that have no SARS CoV2 antibody; if it is not effective against this strain the current advice will need to be changed to more effective alternatives. A lot to think about but, with greater care among the general public to limit spread of disease (masks, distance, handwashing etc) there is yet time to complete the work and boost the level of immunity across the population. Time for all of us to play our part.”


Dr Peter English, Retired Consultant in Communicable Disease Control, Former Editor of Vaccines in Practice, past Chair of the BMA Public Health Medicine Committee, said:

“This is an updated version of the comment I sent on 28 Nov.

“It is probably sensible to decrease the time between 2nd vaccine and booster to 5 months. It will take time to establish the optimum intervals for Covid vaccines. In the meantime there may be a trade-off between getting people immune quickly, and getting the best possible immune response. Longer intervals generally lead to a better immune response; but there’s a “law of diminishing returns” effect. I doubt that there is a lot of difference, immunologically, to a five-month – or possibly even a 3- or 4-month – interval, and a 6-month interval between second and third doses.

“I believe that it is sensible to extend the age range of those who can have boosters to all adults. It has become clear that two vaccine doses provide good protection against severe illness from the original and delta strains; but to provide good protection against infection (and thus the ability to infect others) you really need three doses.

“If the vaccines are less effective against the omicron variant, this will be even more true.

“We know very little about the efficacy or effectiveness of vaccines against the omicron variant. It has become more common in a part of South Africa where vaccine uptake is extremely low, so we could not expect to observe much effect of vaccination. (Unless there are data from the region comparing the relatively few people who have been vaccinated and those who haven’t – I am not aware of such data, but they might exist; South Africa does very good epidemiology.)

“It is likely that vaccines will have some efficacy against the variant – in a sense, we have to work on the assumption that they will, because if they do, we can’t wait to find out. If they don’t – well, at least we’ll have better protection against existing variants.

“Each dose of vaccine boosts antibody levels; and, if antibodies can neutralise this new variant, but less effectively, higher antibody levels can be expected to be more effective. In addition, extra (“booster”) doses can enhance the tightness with which antibodies bind to the virus, and broaden immunity to provide better cross-protection against variants.

“The cellular immune response to vaccines helps broaden immunity, increasing protection against variants.

“We expect that existing vaccines will have some efficacy against the omicron variant, albeit perhaps not as much as against existing variants. If it does, vaccinating children will help protect them, directly, against the effects of the disease and (at least as importantly, perhaps more importantly) its sequelae (organ damage, Long Covid, as well as educational disruption as children are ill and others have to self-isolate…). And if it helps reduce transmission it will help with the indirect effects as fewer of their family members and teachers get ill.

“We know (based on hard evidence) that increasing the numbers of those vaccinated and boosted will enhance our protection against existing variants.

“If vaccines have any efficacy against the omicron variant (as we think it almost certainly will), then it will help against this variant too.

“Thus far, however, there is very little hard evidence about the efficacy of vaccines against this variant.

“The theoretical estimates of possible changes in efficacy, based on knowledge of the specific mutations, are based on evidence, but it is never entirely clear how accurate such estimates will be until we see real-world effects. It is too soon to have such real-world observational data on case rates in people with different levels of vaccination.”



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



Declared interests

Dr Peter English: “Dr English is on the editorial board of Vaccines Today: an unpaid, voluntary, position. While he is also a member of the BMA’s Public Health Medicine Committee (and its chair until Oct 2020), this comment is made in a personal capacity. Dr English sometimes receives honoraria for acting as a consultant to various vaccine manufacturers, most recently to Seqirus.”

None others received.

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