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Covid-19 vaccines for kids under 5 – Expert Reaction

US health authorities have given the green light to mRNA Covid-19 vaccines for children under five and will be made available there, starting this week.

The paediatric versions of the Pfizer and Moderna mRNA vaccines for Covid-19 use the same technology as their adult counterparts, but are being offered at smaller dose sizes and with a different number of shots for the youngest kids.

The SMC asked experts to comment on what the latest data say about vaccinating this age group and the implications for Aotearoa New Zealand.

Dr Dianne Sika-Paotonu, Immunologist, Associate Dean (Pacific), Head of University of Otago Wellington Pacific Office, and Senior Lecturer, Pathology & Molecular Medicine, University of Otago Wellington, comments:

FDA / CDC authorisation

“On 17th June, 2022, the USA Food and Drug Administration (FDA) authorised emergency use of the Moderna Covid-19 Vaccine and the Pfizer-BioNTech Covid-19 Vaccine for the prevention of Covid-19 to include use in children down to 6 months of age. The FDA’s independent Vaccines and Related Biological Products Advisory Committee was convened and consulted, giving their support to these authorisations.

“The vaccine committee from the Centers for Disease Control’s (CDC), have also given their approval for the Pfizer-BioNTech and Moderna COVID-19 vaccines for children aged 6 months and older.

“The conclusions reached were that these Covid-19 vaccines are safe and effective for children aged 6 months and older, and that the benefits of their use outweigh any possibly harms in this context, giving protection from severe illness, hospitalisation and death from Covid-19.

“The CDC director Rochelle Walensky has now formally recommended both Covid-19 vaccines for children aged 6 months and older with vaccinations in the USA to begin the week starting 20th June 2022.”

The Pfizer-BioNTech’s paediatric Covid-19 vaccine

“The Pfizer-BioNTech’s paediatric Covid-19 vaccine is an mRNA vaccine, designed for children aged 6 months to 4 years of age. It is given in three doses, each lower than the adult dose, at 1/10 of the adult dosage. The first two doses are given with a 3-week gap, and the third dose given at least 2 months later.

“A study assessing vaccine effectiveness for the Pfizer-BioNTech’s pediatric COVID-19 vaccine, analysed immune responses between 220 children aged 6 months to four years, compared to 170 adolescents aged 16 – 25 years.

“The results showed that the immune responses generated by the 220 children aged 6 months to 4 years after receiving the Pfizer-BioNTech’s pediatric Covid-19 vaccine, was comparable to that generated in the 170 adolescents aged 16 – 25 years after receiving their higher doses of the Pfizer-BioNTech COVID-19 vaccine.”

Moderna paediatric COVID-19 vaccine

“The Moderna paediatric Covid-19 vaccine is also an mRNA vaccine and designed for children aged 6 months – 5 years of age, given instead in 2 doses, with each lower than the adult dose, at 1/4 of the adult dosage. The 2 doses are given with a 4 week gap, with no 3rd dose needed.

“A study involving 5,400 children at a time when the Omicron variant of the SARS-CoV-2 virus was widespread in the USA, showed that after receiving the Moderna’s paediatric Covid-19 vaccine, vaccine efficacy against developing Covid-19 in those aged 6 months – 2 years was 50.6%. For those children aged 2 – 5 years, the vaccine efficacy against developing Covid-19 disease was 36.8% with the Moderna’s paediatric Covid-19 vaccine.

For noting

“Ongoing studies and monitoring for both the Pfizer-BioNTech’s and Moderna pediatric Covid-19 vaccines will continue.

“US data from the CDC reportedly indicates more than 2,000,000 COVID-19 cases in children aged 4 years and under, and more than 440 deaths have been reported in this same age bracket since the start of the Covid-19 pandemic.

“Hospitalisation figures along with reinfections have surged with the spread of the Omicron variant of the SARS-CoV-2 virus.”

Aotearoa New Zealand

“Here in Aotearoa New Zealand, Omicron is still circulating. Daily reported Covid-19 case figures still high, and continuing to place added strain and serious pressure onto our health and support systems in Aotearoa New Zealand.

“Approximately 100 deaths associated with Covid-19 are being reported each week, and a growing total of 1415 to date – sympathies and condolences respectfully extended to all family, whānau and kāinga at this time. The risk of further waves of Covid-19 remains.

“Of those affected by the current outbreak in Aotearoa New Zealand, a total of 356,499 or 29% (nearly 1/3) were children, tamariki and tamaiki and rangatahi aged 19 years and under, comprising 13% of all hospitalisations.

“Masks and proper ventilation within the education setting remain important for protection, particularly with children, tamariki and tamaiki aged 5-11 years still need to be vaccinated against Covid-19.

“Regular childhood vaccine schedules (non-Covid-19) for children tamariki and tamaiki in Aotearoa New Zealand have been significantly affected by the Covid-19 pandemic. As a result, there is potential risk of outbreaks for whooping cough, measles and other illnesses that could be prevented. A resurgence of influenza and the respiratory syncytial virus (RSV) could also possibly occur.

“Although Covid-19 has been a key focus over the past two years, it is important to remember that all childhood vaccinations are still important.

“During the Covid-19 pandemic, there has been limited exposure to other viruses such as the influenza virus here in Aotearoa New Zealand, meaning there is potential risk of upcoming influenza outbreaks moving into winter. We now have more of the Influenza vaccines here in Aotearoa New Zealand being made available for people – these are much needed right now.

“Immunity gaps currently exist in Aotearoa New Zealand as we move into the winter months and we need to be prepared. This includes for children, tamariki and tamaiki aged 5-11 years who still need to be vaccinated against Covid-19.

“If the Pfizer-BioNTech and Moderna paediatric Covid-19 vaccines are approved for use in those aged 6 months to 4/5 years in Aotearoa New Zealand, this youngest cohort will have had the least time of any group to get vaccinated. The initial strong demand for the paediatric Covid-19 vaccine has been encouraging, however vaccination efforts will need to continue.”

No conflict of interest.

Professor Peter McIntyre, medical advisor, Immunisation Advisory Centre, and Department of Women’s and Children’s Health, University of Otago, comments:

“US data show that COVID-19 is ranked 4th-5th in causes of death across the six months to 12-year age group, but this is on a background of low death rates in these age groups.

“Among children less than 5 years of age, the highest death rate from Covid-19 is in infants less than 6 months of age who can only be protected by maternal immunity, as is the case for the flu. Maternal immunity for flu is worth emphasising just now (see my later comments below).

“Both the Moderna (two doses) and Pfizer (three doses) mRNA vaccines for Covid-19 were considered by the Advisory Committee on Immunization Practices (ACIP) of the US CDC. (Medsafe just recently provisionally approved the Moderna vaccine for people 12 years and older here in New Zealand on 17 June.)

“The Pfizer vaccine approved in the US for children six months to four years of age is a 3mcg dose, which is less than a third of the dose for 5-11 year olds (10 mcg). A third dose (given eight weeks after the second dose) was required to achieve neutralisation titres adequate for activity against Omicron.

“Data for 5-11-year-olds show, as in older age groups, show that vaccine effectiveness (VE) is higher as disease severity increases. That is, VE against hospitalisation was higher than VE against emergency department attendance, which was higher than for any infection with symptoms. VE was more than 80% for protection against the most severe disease due to COVID – multi-system inflammatory disease (MISC) and requirement for ICU admission.

“In the US context, where the flu season in winter 2021-22 was worse than the all-time low in winter 2020-21 but still low compared with previous years, flu mortality in their spring season is lower than mortality due to COVID among kids ages six months to four years.

“However, in the New Zealand context, flu is currently ripping along, and Omicron is heading down, so flu is currently a much bigger risk. It is important to emphasise that the flu vaccine is available free for kids between six months and five years who have a history of significant respiratory illness and for older children with severe medical conditions. For other kids, the flu vaccine has to be purchased but it would be a good precautionary move to do right now.

“In the US, more than half the children hospitalised with Omicron have underlying conditions, although kids with these conditions are probably only about 5% of total kids in this age group. This is the same group for whom the flu vaccine is free.

“Take-home messages:

  • For children 6 months to 4 years, the focus for Covid-19 vaccination should be on those at greatest risk of severe outcomes. This is particularly children living with Down’s Syndrome or other chromosomal anomalies, severe heart or respiratory disease or severe disability from any cause.
  • Death from Covid-19 infection is extremely rare in this age group. Children younger than six months are more at risk than kids six months to five years. There is no published data on protection from maternal COVID vaccination, but just like for flu, we would expect maternal vaccination would protect the youngest infants against severe Covid-19.
  • The first priority now is the flu vaccine, especially for children at risk, and for pregnant women (flu vaccine is free for these women).”

Conflict of interest statement: The Immunisation Advisory Centre (IMAC) has a contract with the Ministry of Health to delivery education and training to the healthcare sector for COVID-19 vaccines. Professor McIntyre is a member of the Ministry’s COVID-19 Vaccine Technical Advisory Group but this statement should not be taken to represent any policy position on the part of the Ministry.”