Explained | Why kids need separate trials for COVID-19 vaccine, how are trials conducted, and enrollment challenges

Source: Reuters

Source: Reuters

US biotech company Moderna on March 16 announced that it has started testing COVID-19 vaccine on children as young as six months old and up to 11 years.

In the phase 2/3 trial, Moderna will be testing the mRNA vaccine on healthy children in the US and Canada.

Moderna estimates that 6,750 participants will ultimately be enrolled for the trial, according to its trial recruitment website.

It isn’t Moderna alone. Pfizer expects to begin a clinical trial on children aged 5-11 years, and AstraZeneca-Oxford University on children aged 6-17 years.

In fact, Pfizer’s COVID-19 vaccine became the one to be given to some older children with underlying conditions in Israel. Some 600 children, aged between 12 and 16, have been given the vaccine, and early results reported in The Guardian have indicated no serious side effects.

In India, Bharat Biotech has approached the Drug Controller General of India (DCGI) seeking permission to test its COVID-19 vaccine, Covaxin, on children aged between 5 and 18 years.

The expert panel of the Central Drugs Standard Control Organisation (CDSCO) has asked the company to produce efficacy data on adults before seeking permission to test Covaxin on children. With interim trials showing about 81 percent efficacy, Bharat Biotech is hoping to get permission to go ahead with the trial.

Here is an explainer on the need for separate COVID-19 vaccine clinical trials for kids, how they are conducted and how difficult it is to enrol children.

Do children need a COVID-19 vaccine?

Children tend to have mild COVID-19, compared to adults. Most COVID-19 cases among children are asymptomatic. Their hospitalisation rate is also very low. There isn’t a clear answer as to why children are not so severely affected as adults. But experts say that children’s immune systems interact with the virus differently than adults’.

Children play an important role in transmitting the virus. Experts say vaccinating children can help suppress overall transmission, generate herd immunity, stop evolution of new variants, and enable them to get back to school more confidently.

Why do children need separate trials?

Their bodies work in very different ways and often undergo many changes as they grow towards adolescence and adulthood. Children, depending on their age and body size, also require different dosages and formulations.

How are children tested?Before a vaccine or a drug is tested on children, they are first tested for safety and effectiveness in adults. Then that particular vaccine or drug will be adapted for children, through a process called dose escalation and de-escalation. Moderna’s study will have two parts.

In the first part, children aged 2 years to less than 12 may receive two doses of 50 or 100 micrograms each. Those under 2 years may receive two shots of 25, 50 or 100 micrograms. The first children inoculated will receive the lowest doses and will be monitored for reactions before later participants are given higher doses. Following that, they will do bigger Phase III studies with more children to determine longer-term effectiveness and safety.

How difficult is it to enrol children?

Children, especially the younger ones, are harder to enrol due to safety and ethical concerns. Given that children have young and maturing immune systems, there is always the risks of them reacting differently, eliciting a surprise side effect. To be sure, vaccine developers do conduct animal trials, especially on infants and baby rhesus macaques, to understand safety implications.

A senior virologist, who was part of the Rotavirus vaccine clinical trial in India, told Moneycontrol on condition of anonymity that testing of vaccines among children generally takes a lot of effort to convince parents and get their consent.

“Why would parents want their children to be part of clinical trials? It’s a sensitive matter. It takes time and patience to win the confidence of parents.  That’s the reason pediatric trials take a long time,” the virologist said.