During the COVID-19 pandemic, immunisation of infants has been a highly contentious and confusing issue. From initial advice that children would be less severely affected, to the FDA’s emergency-use-authorisation of the BNT163b3 and the mRNA-1273 vaccines in June 2022, public health messaging has been mixed. Powerful rhetoric surrounding vaccinating children has also had a worrying effect on routine immunisations. However, a recent study published in Science Translational Medicine by researchers in the US suggests that, following “safe and immunogenic” vaccination, antibodies against variants of concern (VOC), as well as T-cell responses, “persisted for 12 months”.  

The study in context 

SARS-C0V-2 has infected “close to 600 million” and caused “more than 6 million deaths”, the study reports. Although vaccines were developed in record time, we continue to engage with variants and widespread infection, dangerously coinciding with an increase in other disease infections. Furthermore, the authors note that vaccination has not been widely accepted, for a variety of reasons.  

Children younger than 5 years old were originally excluded from vaccination due to “stringent age de-escalation clinical trial protocols” and initial data about infection. However, COVID-19 can cause “severe disease” and death in children, and the emergence of the “more transmissible” variants increased disease incidence in the paediatric population. Neonates were “one of the most affected age groups”. Despite “controversy”, recent data demonstrate the “immunogenicity and efficacy of mRNA SARS-CoV-2 vaccines” at lower doses.  

As these doses are scaled proportionately to those of adults, and immune responses have been observed to decline over time in adults, it is important to “determine whether vaccine-induced antibody responses are durable and of sufficient breadth to protect against infection” with new VOCs.  

COVID-19 in rhesus macaques  

The research involved two groups of 2-month of rhesus macaques (RMs), at weeks 0 and 4. To establish efficacy at one year after initial immunisation, the 2 groups and an added control group of age-matched non-immunised RMs were “exposed to a high-dose heterologous challenge” with the ‘Delta’ variant.  

7 of the 8 control RMs “exhibited severe interstitial pneumonia and high virus replication in the upper and lower respiratory tract”. By contrast, the vaccinated RMs had “faster viral clearance” and “mild to no pneumonia”.  

Limitations of the study include “relatively small group sizes” and the “short follow-up period after SARS-CoV-2 challenge”. Furthermore, the authors acknowledge that “infant RM studies cannot replace human infant vaccine safety and dosing studies”. However, the similarities in “infant physiology and immune development” support a reasonable comparison.  

What does this mean? 

The authors hope that their results will provide a “valuable contribution to efforts to alleviate” parental concerns. The findings add to current data to “provide strong support to initiate SARS-CoV-2 vaccination in infancy and incorporate new SARS-CoV-2 vaccines into the global routine paediatric vaccine schedules to curb the SARS-CoV-2 pandemic”.   

For more on the safety and efficacy of vaccinating children against COVID-19, come to the World Vaccine Congress in Washington next year.