Messenger RNA (mRNA) vaccines formulated by Moderna and Pfizer are already queued up for purchase by the Indian government. The efficacy of both these vaccines is said to be close to 95 percent however, there is not enough clarity around the effect of these vaccines and whether they can be used for patients with serious underlying health conditions. Here we give you a low down on the safety information made available by CDC and FDA.

Mass vaccination drives against COVID-19 have already begun in various countries and India too, will be in the midst of a similar drive by the time you will read this article. The government has hailed the formulation of vaccines namely Covaxin by Bharat Biochem and Covishield by Oxford-AstraZeneca and the Serum Institute of India (SII).

The purchase of Moderna’s and Pfizer’s vaccines, which are based on mRNA formula, is also being considered by the government. While both these vaccines provide an almost similar efficacy of around 95 percent, their approval by the USA’s Food and Drug Administration (FDA) stays limited to emergency use only. Let us first see how can an mRNA vaccine work against COVID-19.

mRNA vaccine

Messenger RNA or mRNA can make the cells in our body produce substances that enable the functioning of the body. These vaccines contain mRNA strands, which instruct the native cells of the body to produce an altered key coronavirus protein. This very protein triggers an immune response for the body, enabling it to fight the coronavirus strain.

As per a statement issued by the Centres for Disease Control and Prevention (CDC USA):

"Adults of any age with certain underlying medical conditions are at an increased risk for severe illness from the virus that causes COVID-19. mRNA COVID-19 vaccines may be administered to people with underlying medical conditions provided they have not had a severe allergic reaction to any of the ingredients in the vaccine."

This statement was followed up with information for patients of HIV, Guillain-Barre syndrome and Bell's palsy like autoimmune conditions, and all those with a weakened immune system. It mentioned that patients with weakened immune systems and HIV were a part of the group of people who underwent clinical trials of these vaccines and could receive a COVID-19 vaccine. However, there was limited data available pertaining to the safety of these vaccines for patients with these specific conditions.

As per a statement issued by the FDA on 17 December 2020, after the clinical trials where patients were given Pfizer or Moderna vaccines, some experienced Bell’s Palsy. FDA did not call it a side effect of mRNA COVID-19 vaccines, but recommended monitoring all those receiving either of them.

Reuters, the news agency, brought to light the groups that have been anti-vaccination when they referred to these very cases while questioning the safety of these vaccines. However, many experts, the FDA and the CDC maintain that a handful of cases are not indicative of any general side effects.

Going by the announcements made by CDC and FDA, we can say that there is very limited data available on the safety of these vaccines for immunocompromised patients. What we learned from their official statements about the clinical trials is that:

• Four cases of Bell’s palsy emerged from among 30,000+ individuals who received Moderna’s formula during clinical trials
• And four cases of Bell’s palsy were reported from 43,000 participants receiving Pfizer’s vaccine
• As per FDA, the paralysis among the victims was observed between 22 and 32 days post inoculation

The staff of FDA did not conclude if the condition among the victims was caused by vaccination. It announced through a statement, “Currently available information is insufficient to determine a causal relationship with the vaccine.” They also did not expect to see a similar incidence rate in the general population. In fact, the FDA staff clarified that those who have had Bell’s palsy earlier can also receive either of Moderna and Pfizer vaccines.

Moderna’s vaccine for COVID-19 has been approved for emergency use by FDA and due to inadequate data on the Bell’s palsy cases, it has added a caveat on monitoring recipients of the vaccine. The guidance issued by FDA for Pfizer’s vaccine was similar to that for Moderna. Officials of CDC USA reiterated that Pfizer’s formula for COVID-19 doesn’t seem to be the reason behind the four cases of Bell’s palsy.