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This article discusses the scientific evidence that is being used to inform ongoing decision making about which children will receive COVID-19 vaccines in the UK. Content includes the latest understanding of how COVID-19 affects children and their role in transmitting the virus. It also includes the latest data on clinical trials that are taking place to study how COVID-19 vaccines work in children, the evidence that will inform who will be offered vaccination and the possible impacts on children and the wider population.
- Recent debate in the UK has focussed on whether to expand the use of COVID-19 vaccines in children aged 12 years and over. No COVID-19 vaccine is currently approved in the UK for use in younger children.
- New scientific advice does not endorse universal vaccination of all children over 12 in the UK. The latest advice recommends that the Pfizer-BioNTech vaccine should be offered to a wider number of children directly at risk from COVID-19, and to children living with an immunosuppressed person.
- There is very good evidence that children who have COVID-19 are much less likely to develop severe symptoms and much less likely to die from the disease than adults.
- While rare in children, serious outcomes from COVID-19 have been studied in this group. The strongest risk factor is having some underlying health problems, including neurological and cardiac conditions or complex neuro-disability.
- Some children may experience longer-term consequences of a COVID-19 infection (referred to as long COVID), but the prevalence and impacts are not yet fully understood.
- The role that children play in transmission is challenging to investigate and is the subject of ongoing research. Limited evidence suggests that although children may be equally susceptible to infection, they may be less likely to transmit the virus than adults.
- Limited data from a single clinical trial of a COVID-19 vaccine in children that is approved in the UK show that it was effective against preventing disease and no severe adverse events were seen; studies in much larger numbers of children are needed to further explore vaccines’ safety in this group. Some data on this is emerging from international childhood vaccination programmes.
- Preliminary data from population surveillance in other countries has suggested that Pfizer/BioNTech and Moderna vaccines are associated with an increased risk of inflammation of the heart (myocarditis and pericarditis) particularly in adolescent boys; although the absolute risk in this group still appears to be low.
- Producing scientific advice to Government about whether to immunise children (and if so, which are the priority groups) is complex, requiring assessment of the risk and benefits not only to children but also the wider population. This is in the context of limited data and the changing dynamics of the progression of the pandemic.
- There is good evidence that parents in the UK are broadly in favour of immunising children against COVID-19. A survey of adolescents (16 and 17 year olds) indicated similar attitudes.
Scientific advice to Government on immunising children
While the Medicines and Healthcare products Regulatory Agency (MHRA) approves medicines and vaccines for use in the UK, the decision about who to offer them to and how to use them is made by the Government.
An independent scientific committee called the Joint Committee on Vaccination and Immunisation (JVCI) advises the Government on whether an approved vaccine should be used, which vaccines should be used in which groups and on dosing schedules. The JCVI reviews ongoing immunisation programmes, amending its advice as the scientific evidence develops. As health is a devolved matter, Northern Ireland, Scotland and Wales make their own policy decisions on immunisation, but they usually follow the JCVI’s scientific advice.
Until 19 July 2021, approved COVID-19 vaccines were offered to all adults aged 18 years or over. There was also JCVI advice to guide clinicians’ decisions on using a COVID-19 vaccine to protect vulnerable children. That has applied since the COVID-19 immunisation programme began in 2020, and was updated on 19 July 2021. This advice is discussed later.
It is anticipated that the JCVI will continue to review its advice on immunising children against COVID-19 as further research emerges about approved vaccines’ safety profiles in children and as the epidemiology of the infection in the population evolves.
COVID-19 and related illness in children
Most children infected with the SARS-CoV-2 virus, which causes COVID-19, are asymptomatic or have mild COVID-19 illness. Mild COVID-19 in children typically includes fever and cough, as well as broader symptoms such as abdominal pain, nausea, headache and sore throat. Overall, children are less likely than adults to develop severe illness or to die from COVID-19. Preliminary data suggest this pattern also applies with newer variants of the virus.
Rare outcomes of COVID-19 in children
Nonetheless, a small minority of children have experienced severe illness, and small numbers have died due to SARS-CoV-2 infection. These children had either acute COVID-19 illness such as pneumonia, or they had a rare delayed inflammatory syndrome called Paediatric Inflammatory Multisystem Syndrome Temporally Associated with SARS-CoV-2 (PIMS-TS; other terms are used to describe this syndrome in other countries).
Rates of death from COVID-19 or PIMS-TS in children in England have recently been quantified using data from the National Child Mortality Database (NCMD) linked with other data sources. During the first year of the pandemic (March 2020-February 2021), 25 children (under 18 years old) were found to have died for these reasons in England; 22 of these children died from acute COVID-19 and 3 died from PIMS-TS. This corresponds to a COVID-19/PIMS-TS mortality rate of 2 in 1 million in all children and an estimated 5 in 100,000 in those infected.
Risk factors for serious outcomes in children
Risk of severe illness and death due to COVID-19 or PIMS-TS appears to be higher in children who have underlying health conditions. Within children admitted to hospital with COVID-19, underlying conditions were associated with critical care admission and death. Having a neurological or cardiac condition was linked with the greatest increased risk. In the NCMD study, the commonest underlying condition in children who died from COVID-19 was complex neuro-disability (13 out of 25 children), and many of these children also had a respiratory condition (8 out of 13 children). However, children who were severely unwell or died due to COVID-19 represented a small proportion of all children with severe illness or who had died in these comorbidity groups.
Other possible risk factors for severe illness and death due to COVID-19 or PIMS-TS include age and ethnicity. Within children admitted to hospital due to SARS-CoV-2, older children (mostly grouped as age 10-17 years) and neonates (within 1 month of birth) have been found to be more likely than young children to require critical care or to die. While these increased risks in neonates were similar to those seen in children hospitalised for other reasons, the increased risks in older children were unique to those admitted due to COVID-19.
Additionally, Black and Asian ethnicity have been found to be associated with critical care admission and death in children hospitalised due to SARS-CoV-2. These increased risks in Black and Asian children were also seen in children admitted for other reasons. Despite these increased relative risks, the absolute risks of severe illness and death due to COVID-19 were still extremely low also in older children, neonates, Black children and Asian children.
Long term effects of COVID-19 in children
The long-term effects of COVID-19 infection in children have not yet been comprehensively investigated. Some children experience symptoms that seem to persist, including syndromes termed ‘long COVID’. The prevalence of these symptoms in children is lower than in adults in UK Office for National Statistics data, but varies in other data sources. This highlights the need for further research, which is ongoing.
Role of children in transmission
Understanding the role that children play in transmitting the virus is of significant policy relevance, relating to measures that limit the opportunities for transmission in the settings where children mix with other children and adults. Information about transmission is also important for planning immunisation programmes because vaccines can limit transmission.
Emerging evidence suggests that children may be as susceptible to infection with the SARS-CoV-2 virus as adults, but research has been limited and this is a complex topic to investigate. Although early studies that tested contacts of COVID-19 cases found that children were less likely to become infected with SARS-CoV-2 than adults, some experts think that these results can probably be explained by biases due to asymptomatic infected children being under-represented in studies. More recent population-based studies that tested for current or past COVID-19 infection have mostly found no difference in infection rates between age groups.
Limited evidence suggests that children may be less likely to pass on the virus than adults, but again investigating this topic has been challenging and results have varied. Research does suggest that the spread of COVID-19 is low in schools when appropriate mitigation measures are in place. For example, Public Health England undertook enhanced national surveillance in educational settings in June-July 2020, and found that most index cases linked to outbreaks were in staff members rather than students. Additionally education staff have not been found to have higher occupational risk of severe COVID-19 illness or death, compared with other adults of the same sex and age, although this topic is particularly difficult to investigate. Most research discussed here was conducted prior to the emergence of the highly transmissible Delta variant, and further research is needed to understand subsequent patterns of transmission.
Studies in adults have found that COVID-19 vaccines seem to reduce transmission. For example, Public Health England research reported that adults with COVID-19 who had been vaccinated were 40-50% less likely to transmit infection to household contacts compared to unvaccinated adults with COVID-19.
However, because transmission patterns in children and adults differ, it is unclear to what extent COVID-19 vaccines would reduce transmission between children and between children and adults, although it is unlikely to be greater than the reduction reported for adults.
Clinical trials of COVID-19 vaccines in children
The research about how COVID-19 vaccines work in children is more limited compared with data about adults, although multiple studies are underway. They will reveal how children’s immune systems respond to the vaccine and give important safety data.
Most trials of the efficacy and safety of COVID-19 vaccines have been undertaken in adults. The Pfizer/BioNTech vaccine trials in adults also included young people aged 16-17 years. These trials of approximately 43,000 people aged 16 years and over found that the vaccine had good efficacy and safety across age groups.
More recently, a COVID-19 vaccine trial has been conducted in children aged 12-15 years. Because this study involved fewer participants who have been followed up for a shorter time-period, less is known about the efficacy and safety of vaccines in this age group than adults.
The study trialled the Pfizer/BioNTech SARS-CoV-2 vaccine versus placebo in 2,260 children aged 12-15 years. After two doses, there were no cases of COVID-19 illness in the vaccine group and 16 in the placebo group, giving a vaccine efficacy of 100%. As for adults, in this trial the vaccine had a favourable safety and side effect profile in 12-15 year olds. The most common adverse effects were short-lived mild-moderate symptoms, including injection site pain (in 79-86% of participants), fatigue (in 60-66%) and headache (in 55-65%). There were no vaccine-related serious or severe adverse events. Several other COVID-19 vaccine trials are underway in children, including younger children under 12 years old.
Case reports and population vaccine surveillance has identified an increased risk of inflammation of the heart muscle or lining (called myocarditis or pericarditis) after Pfizer/BioNTech and Moderna SARS-CoV-2 vaccines. The US Centers for Disease Control and Prevention (CDC) data suggests that the risk is highest in adolescent boys, although the absolute risk remains low in this age group, with a rate of 63 cases of myocarditis per million vaccine doses. The CDC concluded that the benefits of vaccination still clearly outweigh the risks, and the JCVI considered this concern when making their recent updated recommendations (outlined below).
Surveillance data has not highlighted any other serious adverse events that might be more common in children than adults.
Vaccines approved for use in children
In the UK, the MHRA approved the Pfizer/BioNTech SARS-CoV-2 vaccine for use in people aged 16 years and over in December 2020, and in those aged 12-15 years in June 2021. All other licensed SARS-CoV-2 vaccines (Oxford University/AstraZeneca, Moderna, and Janssen) have been approved for use only in adults aged 18 years and over by the MHRA.
Since the UK COVID-19 immunisation programme began in December 2020, the JCVI has recommended vaccination only for a small group of children aged 12 years and over who are at higher risk of infection. These recommendations have been implemented as detailed in Public Health England’s publication about national immunisation programmes called the Green Book. In view of the COVID-19 vaccination programme progressing in adults, the JCVI reviewed recommendations for vaccinations in children.
On 19 July 2021, the JCVI published advice that COVID-19 vaccination should be extended to cover additional groups of children, and these recommendations have been accepted. The updated UK COVID-19 immunisation plan for children announced by the Government on 19 July is summarised here:
- In 12-15 year olds with certain underlying health conditions: the Pfizer/BioNTech SARS-CoV-2 vaccine should be offered to those with severe neuro-disabilities, Down’s syndrome, immunosuppression, profound and multiple learning disabilities, and severe learning disabilities if on the learning disability register. This update was announced on 19 July 2021. Previously since December 2020, vaccines were considered only for those with severe neuro-disabilities who tend to get recurrent respiratory tract infections, particularly those who spend time in specialised residential care settings.
- In 12-15 year olds who are household contacts of an immunosuppressed person: the Pfizer/BioNTech SARS-CoV-2 vaccine should be offered to protect the immunosuppressed person. This update was announced on 19 July 2021.
- In 16-17 year olds: the Pfizer/BioNTech SARS-CoV-2 vaccine should be offered to those who are clinically extremely vulnerable (in priority group 4 of the UK Phase 1 COVID-19 vaccination programme that focussed on adults) and should be offered to those in at-risk groups with certain underlying health conditions, or who are a household contact of a person with immunosuppression or a carer (in priority group 6). This recommendation has been in place since December 2020.
- In 17 year olds within 3 months of their 18th birthday: vaccines should be offered as for adults, to ensure good uptake of vaccine in newly-turned 18 year olds. This update was announced on 19 July 2021.
- In other children: COVID-19 vaccines are not currently recommended.
These recommendations will continue to be reviewed by the JCVI.
Vaccine use in children elsewhere in the world
Several countries have taken a different approach to the UK and are vaccinating all children aged 12 years and over. Canada and the USA were among the first to approve and begin to roll out the Pfizer/BioNTech vaccine for all children aged 12 years and over from May 2021. Additionally, some European countries, including France and Italy, have since approved and started to provide the Pfizer/BioNTech vaccine for all children aged 12 years and over. These decisions were based on the evidence described above, particularly the clinical trial in 12-15 year olds, as well as country-specific infection and vaccination rates. These countries’ advisory committees concluded that the benefits of vaccinating adolescents outweigh potential risks.
However, other countries have adopted the same approach as the UK, including Germany, by recommending the Pfizer/BioNTech vaccine only for children aged 12 years and over who have certain underlying conditions. These decisions were based on the same evidence, but advisory committees came to a different conclusion, that the benefits of vaccination do not outweigh risks for most adolescents, only those most likely to become seriously unwell or die due to COVID-19 infection.
Complexities of scientific decision making on immunising children
The decision about whether to offer an approved COVID-19 vaccine to children aged over 12 years is complex. Scientific experts review all available research to determine what the benefits of vaccinating children are and to weigh this up against known or possible risks. This evidence continues to accumulate, with important data emerging as other countries begin to vaccinate adolescents (children aged over 12 years) against COVID-19 as part of national programmes.
One of the most important factors is an assessment of the direct health benefits and risks to children from vaccination. Since children are less likely to be seriously affected by COVID-19 than adults, the balance between benefits and risks is not the same. For example, the risks from COVID-19 for those aged over 80 years far outweigh the very small risk associated with a serious vaccine side effect. The protection offered by vaccination is a clear benefit that further outweighs the risk for this age group. For a child, a vaccine offers minimal benefit, because they are much less likely to be seriously affected by COVID-19. Therefore, the balance between benefits and risk is very different, as the direct health benefit to otherwise healthy children is very small.
Long COVID is a term used to describe a syndrome where people experience a range of symptoms that persist after the initial infection has resolved. The risk to children from long COVID is not yet fully understood, but some experts suggest that the small risk from vaccination outweighs the potentially greater risk posed by as yet unknown long-term health consequences of infection.
Apart from the data describing the direct medical impacts, scientists advising the government also consider other factors. Vaccinating children could offer other indirect benefits to children themselves or to the wider population. For example, if immunising children contributes to reducing overall levels of infection, this could help to minimise disruption to schooling and other activities that support children’s physical and social development. However forthcoming policy changes to end the use of bubbles in schools and self-isolation may mean that this potential benefit no longer applies.
Another potential benefit is to what extent immunising children plays a role in minimising transmission of the virus in the settings where children spend time, such as in their own homes and in the wider community. This could also be a benefit that declines in prominence as more adults in the population are directly protected themselves through vaccination. It is also possible that as more adults are fully immunised in the coming months, infections will be concentrated in children, adding further complexity to the risk-benefit assessment. Immunising children who share a household with vulnerable adults could offer additional protection to this group.
Immunising children who are at most risk from COVID-19
Some children designated as clinically extremely vulnerable (CEV) to COVID-19 were advised to shield at certain points in the pandemic in 2020. Current advice is that children in this group are not currently recommended for vaccination, apart from one group (older children with severe neuro-disabilities who need residential care). Overall, children under 16 who are CEV are at low risk of serious outcomes or death from COVID-19.
Decisions about whether to extend immunisation to this group of children, or other children who may be at greater risk from COVID-19 is an ongoing question. Improving the understanding of which children might be at most risk (and therefore a potential priority immunisation group) is seen as an urgent research priority. The latest JCVI advice to immunise additional groups of children with underlying health conditions reflects how advice evolves as more research become available.
What are the arguments against immunising children against COVID-19?
The potential benefits of immunising children are much smaller compared with adults because children are much less likely to experience serious disease. There is less data on the risks of using COVID-19 vaccines in children compared with adults. As data from clinical trials in adolescents is limited, there is less information about potential rare adverse events in children. Data about the possible risk of these is clear only once vaccines are used in much larger numbers of people.
From an ethical perspective, one argument is that the supply of vaccine that could be used in children would offer greater overall health benefits if it were used in adult populations elsewhere. It is suggested that greater net benefit would be derived by using vaccine in countries who have less access to vaccine supplies or less developed infrastructure to immunise their most vulnerable groups. However given the large volumes of vaccine that would be needed to achieve higher global vaccine coverage, it is suggested that both aspects could be met by increasing supplies and delivering on commitments to countries that would benefit from international support.
Furthermore, some suggest that this approach would also indirectly protect the UK population, since improved global vaccine coverage could limit the evolution of emerging SARS-CoV-2 variants that would very likely be seeded into the UK. New viral variants can have different properties that make them more transmissible, potentially cause more serious disease or lead to rapid growth in infections. Existing vaccines may also be less effective against new variants. While new vaccines can be developed to overcome this, it takes some time before they are ready to be offered in immunisation programmes.
Public attitudes to immunising children
Data on attitudes comes from detailed research studies and surveys, with surveys of parental attitudes and more recently views from older children themselves. Overall, evidence indicates that parents are broadly in favour of COVID-19 vaccination, as are older children themselves.
A detailed high quality research study of parental attitudes was conducted in England and published in November 2020, before COVID-19 immunisation began in the UK. It reported that most parents would likely accept a vaccine for their child (48% said definitely, 41% were unsure but leaning towards yes). Study participants from Black, Asian, Chinese, Mixed or other ethnic backgrounds were three times more likely to refuse a COVID-19 vaccine for their children than participants from White backgrounds.
This positive sentiment is reflected in more recent data. The Office for National Statistics collects data about the public’s attitudes to COVID-19 vaccination in regular surveys. The latest data on attitudes was reported in May 2021. Parents of primary and secondary school age children were also asked whether they would want their child to be immunised against COVID-19. Nine in 10 parents were broadly in favour:
- parents of primary school aged children:
- 43% said they would definitely want their child to be immunised
- 46% said unsure but probably yes
- 4% said they would definitely not want their child to be immunised
- parents of secondary school aged children:
- 53% said they would definitely want their child to be immunised
- 35% said unsure but probably yes
- 3% said they would definitely not want their child to be immunised.
In the ONS’s most recent data update, 16 and 17 year olds were also asked about the likelihood of accepting the offer of vaccination. 86% said they were fairly or very likely to have the vaccine if offered, while 14% said they were unlikely to have the vaccine if it was offered.
Attitudes to vaccination and the reasons why people refuse or are hesitant about accepting a COVID-19 vaccine are discussed in a POST article published in July 2021. This is driven by the interplay between the perceived benefits and risks of immunisation.
The main reasons cited by parents for not wanting a child to receive a vaccine were a wish for more information on the long-term side effects, and concerns that not enough research has taken place, and about the safety and side effects of COVID-19 vaccines. This reflects similar attitudes from much larger international population surveys, and data from reviews of multiple studies where confidence in the safety and effectiveness of COVID-19 vaccines drives people’s willingness to be immunised, alongside the wish to protect oneself and others.
The Royal College of Paediatrics and Child Health has published an evidence summary of various aspects of COVID-19 and children which is updated regularly, as well as a statement on the vaccination programme.
POST is grateful to Dr Steph Lewis for co-authoring this briefing and to the Medical Research Council for funding her parliamentary fellowship. For further information on this subject, please contact the co-author Dr Sarah Bunn.
POST would like to thank Professor Beate Kampmann (Professor of Paediatric Infection & Immunity and Director, The Vaccine Centre, London School of Hygiene and Tropical Medicine) who acted as external peer reviewer in preparation of this article.
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