Why Isn't the UK Vaccinating Young Children for COVID?

Becky McCall


December 17, 2021

As the UK government’s COVID booster vaccine campaign sees a record number of people booking their shots, news reached NHS England staff to prepare for the mass vaccination of primary school children.

Confirmed UK case numbers of Omicron, the rapidly spreading variant of concern, are rapidly rising, with worries for its high transmissibility as well as its potential to evade vaccine protection. As such, boosters are now being offered to all over-18s by New Year.

But some scientists are also calling for the vaccination to be extended to ensure as many children as possible, including 5- to 11-year-olds, are vaccinated to help prevent Omicron disrupting the new school term in January.

Speaking about the potential vaccination of primary school-age children at last week’s Royal Society of Medicine webinar on Omicron, John Edmonds, OBE FMedSci, epidemiologist from the London School of Hygiene and Tropical Medicine, said that transmission of the Delta wave from autumn onwards, had been concentrated in school-age children, "mostly secondary school age children who I believe are more likely to spread the virus than primary school children." But he added that now, “we see equivalent rates of infection in primary school children".

"From the population perspective it is clear that we need to vaccinate everyone from 5 years up," he said. "However, I do think we need to think about it harder, particularly for young children under the age of 11 because they are much less likely to have severe consequences of Covid, so we need to examine safety signals very carefully."

As the vaccination strategy progressively works down the age groups, 5- to 11-year-olds are certainly next in line, although when that actually happens might not be as simple as some people might think.

Lower Risk of Disease

Data on the Delta and Alpha variants show that as age decreases so the risk-benefit equation shifts. Generally, risk of severe disease and hospitalisation due to COVID-19 is lower across primary school children compared to older children or adults.

Data show that there is also a relatively good demarcation in risk level between primary school and secondary school children, says Shamez Ladhani, MRCPCH, PhD, Paediatric Infectious Diseases specialist at St. Georges Hospital, London.  "The risk is very low in primary school age and younger, and then the risk starts to increase in secondary school children, but a 16-year-old will have a substantially higher risk of Covid than an 11-year old. That gradient is not seen in primary schools to any great extent."

But if primary school children are next for a first course of vaccination, then there are some significant logistical hurdles to overcome first. The Pfizer vaccine likely to be authorised for this age group is different in that it contains only 10 µg of the antigen compared to 30 µg in teens and adults, and has to be purchased separately and cannot just be a dilution of the adult dose. There are also issues around reformulation, supply and administration. "There are no school systems in place for vaccinating primary school children like there are for secondary schools, which have existing vaccination programmes such as for MMR and meningococcal disease."

And all this would need to play out as the nation’s medical workforce is highly focused on delivering one million booster doses per day by year end.

"If we have limited vaccines and limited resources, the question is where do we put that resource? A vaccinated adult still has a higher risk of severe Covid that an unvaccinated child," asks Ladhani, speaking to Medscape UK.

"Prioritisation is key. With a big wave coming then vaccination priority must go to the most vulnerable who need most protection," he asserts. "Optimising vaccination in the highest risk groups will achieve better overall vaccination outcomes than trying to vaccinate everyone regularly all the time."

Length and Type of Protection from Vaccination: Infection or Hospitalisation?

With current COVID vaccines, the argument that vaccinating children to prevent infection (rather than the mantra used for adults that vaccines protect from severe disease and death) struggles to apply.

"Children can still get infected even after vaccination, and they can transmit to others if they get infected. We know that fully vaccinated adults can still get infected and can also infect others," Ladhani stresses, adding that, "Right now, it looks like the current vaccines only give very short-lived, and limited, protection against infection and mild Covid, but hopefully will continue to provide longer term protection against severe disease and death, even with new and emerging variants such as Omicron."

This short-term protection against infection will wane very quickly especially if children only have one dose, and the same will happen after the second dose, adds Ladhani. 

In effect, the only way to stop infection and transmission is children would be to re-boost regularly. “It suggests that if you really want to stop children from both infection, and transmission to others, then we would need to keep giving them regular boosters every few months.”

Ultimately, notes Ladhani, greater clarity is needed about what the paediatric vaccination campaign in the different age groups is trying to achieve. "These vaccines remain highly effective against severe disease, but it is becoming increasingly clear that they are not every effective against infection, transmission or mild disease."

Pfizer Vaccine in Children: Study Outcomes and How it Differs to Adult Vaccine

The most likely vaccine for primary school age children is the Pfizer/BioNTech vaccine for 5-11-year olds, which is already in use in the US, although uptake is very slow.  The ‘kiddie dose’ as it is called in the US, is a 10-µg dose compared to the 30-µg for 12 years and upwards, including adults. The two-dose interval is likely to be around 8-12 weeks in the UK. The child dose is also contained in a different stabilising buffer (tromethamine [Tris]) to the adult version and is colour-coded to avoid confusion with adult doses.

Formulation is important and these differences and the knock-on effects for manufacture and supply could be the limiting factor in any potential roll-out to young children in time to curb the possible effects of Omicron. 

"At the moment, it looks like we will be progressively vaccinating down the age groups as long as vaccine is available," Ladhani points out, who in his role as consultant epidemiologist has overseen much of the UK Health Security Agency’s studies into the dynamics of COVID-19 among school children. 

"The Pfizer vaccine for 5- to 11-year olds is a completely different vaccine which needs to be supplied and stocked separately from the adult vaccines. It cannot just draw on available stocks. It’s all about logistics and delivery as much as timing."

Pfizer/BioNTech data on vaccine effectiveness in 5- to 11-year olds compared neutralising antibody titres after two 10-µg doses, with titres from two adults size doses in 16-25-year-olds and young adults. Vaccine efficacy was 90.7% effective at preventing symptomatic infection in young children[BM1] .

Regarding side effects, swelling and redness at the injection site as well as fatigue and headache were reported.

Myocarditis: Growing Data Looks Reassuring

Despite not being reported as adverse findings in vaccine trials, myocarditis and pericarditis have presented as the main cause for concern after numerous reports of possible cases since vaccination has been rolled out more widely. Rates from vaccine and virus in adults and children are under constant surveillance but vary by country. "They have different surveillance systems and all of them are measuring slightly different things."

"With myocarditis, there are increasingly reassuring data coming through on the immediate outcomes of post-vaccination myocarditis in adolescent young adult males, as more and more children get vaccinated," says Ladhani.

"But the bigger issue is not just the rates which may be very low, but the potential consequences of any long-term damage to the heart which some people may not appreciate," he cautions.  Case numbers may be very few, but if those cases end up with very severe complications, then you are potentially giving those children a lifelong complication. "That could take away a few years of a life," he adds.

Given it is known that SARS-CoV2 infection can cause myocarditis, which is serious, "before implementing a large-scale vaccination campaign you have to be confident of the safety of the vaccine, especially if the benefit to risk ratio is marginal."

“The heart, of all organs, is the one that keeps you alive for the longest, so any damage to the heart now can have very long-term consequences.”

Magnetic resonance imaging suggests there is a significant effect of vaccine-induced myocarditis on the heart, as well as increased levels of troponin in the blood which measures damaged muscle, and inflammatory markers.

"It looks like most cases recover quickly after developing their first symptoms, but we don’t know if there are any permanent effects because that takes time, probably 6 months, before you are confident that’s the heart was exactly the same as it was before."

“If that issue is resolved and there are no problems with the heart after a few months, then it’s okay,” says Ladhani, but “there are already very rare cases of scarring of the pericardium in young adults with post-vaccine myocarditis."

Risk-Benefit of COVID-19 Vaccination in Children

Whether children aged 5-11-years need vaccinating or not, poses a similar question to that addressed by the Joint Committee on Vaccination and Immunisation (JCVI) for children aged1215 years in the summer. "The benefits and risks remain marginal in children," says Ladhani.

The risk of children being hospitalised with severe COVID-19 is very low at around one in 200. Data from the first year of the pandemic (March 2020- February 2021) found that’s 251 children were admitted to intensive care units, while 25 deaths occurred in children with Covid. Ladhani notes that severe outcomes, such as death, are extremely rare but that current data are confounded by admission for COVID-19, or whether the infection was just incidental when children were hospitalised for other illnesses.

"Without a doubt, vaccination should help protect against the very small proportion who might get severe Covid and be hospitalised,” he says, but adds that, “not all, because actually those who end up with severe Covid tend to have multiple underlying medical conditions too."

Whichever way you look at it, there are consequences of mass vaccinating against COVID-19 in children and teens, Ladhani asserts. Not least, it will also delay all the other healthcare measures provided for in terms of other immunisations they receive in schools, because healthcare staff are re-deployed to COVID vaccinations.

"These are more likely to cause long-term problems. Some of the immunisation programmes for children and adolescents have massive herd immunity effects and losing control of them such as with meningococcal ACWY vaccination for teenagers means we will lose our population level protection which in turn could see increases in cases across all age groups – and meningococcal disease, while rare, is associated with high morbidity and mortality."

Peter Openshaw, Professor of Experimental Medicine at Imperial College, London, member of the government’s New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), also spoke about the risk-benefit of child COVID-19 vaccinations at the recent Royal Society of Medicine webinar.

"Recently, for various reasons, it seems that high rates of infection are being seen in school-age children. To my mind the uncertainties of the long-term of infection by SARS-CoV-2, whether adult or child, is much more worrying than the potential medium to long-term effects of being vaccinated. We need to acknowledge that these vaccines aren’t completely benign, and there is a very low rate of transient myocarditis and pericarditis, but to me that is much less of a worry that the complications of catching Covid."

Logistical Hurdles

Mass vaccination roll-outs take a lot of planning. This is true in adults, but much more so in small children.  With the teenagers there was opportunity to piggy-back on existing vaccination programmes, such as those for human papillomavirus (HPV) and meningococcal ACWY, but there is nothing similar in primary schools. "Apart from the nasal flu vaccine, we don’t have school-based vaccination programmes in primary schools, so a 5- to 11-year-olds campaign isn’t straightforward. Trying to do a vaccination campaign in this age group without parents being present too would be unique because they are so young, and we would also need special paediatric trained immunisers in large volumes and very quickly."

Finally, there’s the timing element of it all. “Implementing a full vaccination campaign across all school age children, 5-17 years, in the face of the threat from Omicron, is unlikely to be quick enough,” remarks Ladhani. "It just isn’t feasible to get two doses into children, plus we’re not confident it will protect them against infection, transmission or mild Covid, if that is the goal. If you just want to avert infection numbers in children, then this will be an uphill battle if Omicron turns out to be as transmissible and evade both natural and vaccine-induced immunity, as the early evidence suggests."

COI: Dr Ladhani also works for the Immunisation and Countermeasures Department, UK Health Security Agency, but spoke to Medscape UK in his capacity as a paediatric infectious diseases specialist.


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