What is emergency-use authorisation of Covid-19 vaccines?

It's been almost a year and half since India registered its first coronavirus case. And since then, we have been hearing new terms that define the pandemic's rise and fall. We have also seen a race across the world to produce a vaccine against this virus. A term which has been and is being used very frequently in the field of vaccines is'Emergency Use Authorisation' or EUA.

But what is EUA?

What is EUA and when is it given?

In an emergency to diagnose, treat or prevent serious or life-threatening diseases or conditions, when marketing authorisation is given to an unapproved medical product, or the regulator authorises unapproved use of an approved medical product, it is called EUA.

This is unlike full authorisation, for which the regulator assesses more elaborate data collected over a longer duration of time. 

Now here is what it means for patients. The Indian regulator gave "restricted emergency use” authorisation to drugs like remdesivir. This means the doctor who prescribes the drug has to explain the risks and benefits to the patient and also clearly state that this drug does not have a full authorisation. The patient has to sign a consent form indicating that she or he has understood the implications.

Now, let's look at the process by which a EUA is given.

EUA is never granted based on only phase-1 and -2 clinical trial data (which are necessary to ascertain that the product is safe). EUA is considered only after sufficient efficacy data is generated in a Phase-3 trial. For Covid-19 vaccines, the USFDA has specified that it would consider an application for EUA only if the Phase-3 data show it is at least 50 per cent effective in preventing the disease. This data needs to be generated from over 3,000 trial participants who have been followed up for any serious adverse events for at least one month after all doses have been given.

So why are vaccines being given EUA, not a full authorisation?

The regulator would need long-term immunogenicity data. It means whether the vaccine induces the desired immunity against a disease pathogen from the trials or not. One may produce antibodies against the pathogen now, but it is important to see if the person also develops what we call memory-cell immunity. This means that if exposed to the pathogen after a long period of time he still produces antibodies.

At the moment, no vaccine maker would be able to submit this long-term data. Regulators would thus review this interim data from the trials and decide if the vaccine merits an approval for use during the pandemic. Long-term data would be subsequently submitted to the regulator from time to time to get a full authorisation.

So, after a vaccine gets EUA, it is first made available to the vulnerable population and eventually in the private market for all. Since we are in the middle of a pandemic, the government and policy makers would have a say in the way the vaccine is distributed so as to ensure effective mitigation of the risks to larger populations.