Vaccination against COVID-19 in adolescents. A reality

“Good habits formed at youth make all the difference”. (Aristoteles)

On 4th May, the drug regulatory agency of Canada and on 10th May the Food and Drug Administration of the United States authorised the extension of the emergency use of the BioNTech-Pfizer (COMIRNATY®) vaccine in the 12–15 age group, since in its earlier approval 5 months previously for people aged from 16 years upwards.¹ This vaccine is therefore the first to be approved for the prevention of COVID-19 in adolescents.

On 12th May the Advisory Committee on Immunization Practices of the Centres for Disease Control and Prevention of the United States, following a systematic review of all available data made a provisional recommendation for the use of the vaccine in this age range. The said recommendation was published on 14th May in the Morbidity and Mortality Weekly Report.² The vaccine immediately began to be administered in Canada and the United States to this population group. In the United States parents and tutors of adolescents were encouraged to receive vaccination but the results of several surveys showed that approximately only half of the parents were willing for their children to receive the vaccine (range: 45%–60%).²

The European Medicines Agency (EMA) began to review the request for this extension on 3rd May and it was approved on 28th May. The other three vaccines approved by the EMA (Moderna, Vaxzevria from the Oxford University-AstraZeneca and Janssen) were to be used from 18 years of age upwards. Clinical trials began to be conducted in adolescents, which AstraZeneca stopped, due to the coincidence of the appearance of cerebral venous sinuses thrombosis during the course of vaccination of the general population. Studies had also been initiated with the two Messenger RNA vaccines in children aged from 6 months to 11 years, stratified into three age groups, to cover all paediatric age. These studies were conducted in three different vaccine doses (TenCOVE and KidCOVE Moderna trials).³ In the case of nursing babies under 6 months of age, protection could be obtained through the vaccination of the pregnant women.

Compared with adults, children and adolescents have a low rate of infection and a lower risk of presenting with severe forms of the disease, or requiring hospitalisation, admission to intensive care units (ICUs) or death. However, they may also be infected, get ill and spread the infection in their environment. Children belonging to risk groups and the people living with them should not be ignored. Data from the United States highlight that 12% of all cases of COVID-19 have affected children and over 300 have died.⁴ The Centres for Disease Control and Prevention point out that 21.5% of patients who presented with severe multisystemic hyperinflammatory syndrome, that occurred several weeks after acute infection by SARS-CoV-2, were adolescents aged between 12 and 17 years.² Of the adolescents hospitalised in the United States during the first quarter of 2021 almost a third required ICU admission and 5% required invasive mechanical ventilation.⁵

Secondly, adolescents have to be vaccinated to obtain collective or group immunisation as soon as possible, which in principle, is established at 70% of the population. However, it is increasingly argued that this percentage should be 80%–85%⁶ given that current vaccines probably provide a short duration immunity and do not lead to sterilising immunity. However, at present it is already being demonstrated that vaccines have a certain capacity to reduce infection and especially regarding transmission of the virus from the vaccinated person to a susceptible one, with lower frequency and a lower viral load.

Notwithstanding, there is concern regarding the threat of the appearance of variants due to greater contagiousness, with basic and effectively higher reproduction numbers (R0 and Rt) which may evade vaccine immunity, and this requires a higher proportion of the population be vaccinated. If children and adolescents do not receive vaccines, there will be millions of people keeping an active virus circulation going. The Spanish population aged between 12 and 18 years is 3.4 million, 7.2% of the total population, which is a considerable percentage for increasing collective immunity.

Lastly, in many countries, vaccination is required to restore the stability of the education system in order to keep schools open, with the advantages that this entails for both the adolescents (particularly for their mental health, in addition to the educational and emotional impact) and their parents (due to the labour, economic and social problems school closure may entail). In Spain, according to data from the Ministry of Education and Vocational Training, during the 2020–2021 academic year it was confirmed that cases and outbreaks occurring in this environment were small, with a very low percentage of classrooms (under 2%) being closed due to quarantine confinements.⁷ Infection transmission in schools was low, particularly in children under 12, who almost always caught infection in their own homes. In the teenager the situation changed, due to greater activity and socialising at this age. The way in which primary and secondary schools functioned in Spain has been exemplary, with face-to-face teaching of primary and secondary students adapted to the circumstances of the pandemic.

Child infection rates have been seen to increase with the pandemic. Although this is partly because in the initial phases of the pandemic only severe cases were diagnosed and reported of people who were hospitalised and most of them were adults. Of the different life stages included in paediatrics, adolescence is the one with the most frequent cases of COVID-19. According to the Ministry of Health in Spain, on 15th April 2020,⁸ the figures of incidence in those under 10 years of age and those aged from 10 to 19 years were .3% and .6% of the total cases reported, respectively, and hospitalisation was .2% for each age group, with .4% and .1% in the ICU. These data coincide with those of the first published series in China.⁹ One year later, updating the situation of COVID-19 in Spain on 5th May 2021, among the cases reported from 10th May 2020 onwards (the time when data collection sheets were simplified) the number of cases of those under 15 years of age was 12.8%, and in the group aged 15–29 years, where the first years corresponded to adolescence, this figure was 19.8%. The group of children aged up to 14 years who required hospitalisation was .6% (7.3% of hospitalisation in all ages), and ICU admission was .03%. There were 12 deaths.¹⁰

A high quality, safe, immunogenic, and effective vaccine is available to prevent this disease. Following a clinical trial with 2,260 adolescents aged from 12 to 15, with no evidence of prior infection by SARS-CoV-2, randomly assigned 1:1 to receive a vaccine or placebo (saline solution), with a median follow-up of 2 months, a robust antibody response was observed, with higher immunogenicity to that of the group aged between 16 and 25 of the pivotal (registration) trial (geometric mean of the neutralisation antibody titre: 1239 and 705, respectively). The immuno-bridging comparison data of the vaccine receptors with those of the group aged between 16 and 25 years endorsed vaccine efficacy, which confirmed phase 3 of the clinical trial. Good tolerability to the vaccine was also observed, also similar to that of the comparative age group of immunogenicity. The most common manifestations were tiredness, fever, headache, shivering and injection site pain, and these were more common and intense after the second dose. Clinical efficacy compared with symptomatic disease was 100%. The 18 cases of disease which appeared all belonged to the group which received the placebo and there were no cases among those who had been vaccinated.^2,11

The Moderna laboratory has just requested that the EMA and the FDA extend the use of the anti COVID-19 vaccine to adolescents aged from 12 to 17 years. China has approved the emergency use of CoronaVac manufactured by Sinovac Biotech for children and adolescents aged between 3 and 17 years.

Vaccination strategy in adolescence

Phase one: priority vaccination

Vaccination should be initiated in the following groups:

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  Adolescents from 12 to 15 years with severely high-risk diseases or situations who would be included with these other patients belonging to all ages, in group 7 of the population group to be vaccinated, in keeping with the latest update on vaccination strategy in Spain.¹²

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  Adolescents from 12 to 15 years with severe neurological diseases, who are heavily dependent or who go to centres for people with intellectual disabilities, healthcare centres, guardianship centres or special education centres, which have already been included in the Interterritorial Council of the National Healthcare System. These should be individually assessed, after the doctor has spoken with the parents and the teenager, with a shared medical decision being reached.^13,14 The carers and close contacts of these patients should also receive priority vaccine provision

Phase two: systematic vaccination

Adolescents aged between 12 and 15 years should be systematically vaccinated once vaccination has been finalised in groups of adults where there is a higher risk of hospitalisation, admission to ICU and death.¹⁵ In the 7th update of the Vaccination strategy against COVID-19 in Spain document, dated 11th May,¹² the last group included is number 10, which corresponds to people aged between 40 and 49, with those aged between 12 to 39 as of yet unclassified. This could be a single group or divided into cohorts of 10 years (30–39, 20–29, and 12–19 years). This phase could coincide with the beginning of the next 2021–2022 school year, and if undertaken in the school environment, would foment the obtainment of high vaccine coverage rates.

In a second phase, when the results of the clinical trials with children under 12 years of age are released, strategies to follow in the different age subgroups, from 6 months onwards should be considered with an evaluation of the risk-benefit ratio, the evolution of the pandemic and the availability of vaccines. Once the adult population has been vaccinated, the susceptible population remaining, among which is the child population, will be the one that would keep the virus circulating.

A final reflection

In a globalised world, in the specific situation of the pandemic, vaccines should be an ethical duty, borne out of solidarity, social justice and vaccine equity. Also, it should be remembered that if the whole world is not protected, the countries with high vaccine coverage will not be protected either. Under these circumstances, can the most developed countries use vaccines for their adolescents who do not have a high risk of suffering from serious illness and death, when many countries with low economic resources do not have vaccines to protect their most vulnerable risk groups? The primary need is for vaccines to reach countries with the highest need for them, but we should not forget that adolescents should also be vaccinated. The ethical obligation and principle of vaccine equality must also govern in adolescence.

Financing

This study did not receive any type of financing.