By Roger Chriss, PNN Columnist

Covid-19 vaccine researchers reported good news this week. Pfizer and Moderna both announced encouraging efficacy data and will soon submit applications to the Food and Drug Administration for emergency use authorizations.

Moderna reported that its vaccine was 94.5% effective in a Phase 3 trial of more than 30,000 participants. Similarly, Pfizer’s vaccine had an efficacy rate of over 90 percent, with only 94 confirmed cases of COVID-19 in a study that included over 43,000 volunteers.

Both of these vaccines are based on mRNA technology, a genetic approach to vaccines that directs protein production throughout the body. AstraZeneca took a more conventional approach with its vaccine and just reported promising Phase 2 trial results.

There are of course important questions to sort out, including long-term efficacy and safety. This latter point is particularly important for people with chronic illness.

The vaccine trials have been run with volunteers, who may be more health conscious and healthier than the population at large, and people with specific disorders are excluded. As a result, safety issues for people in treatment for active cancer, people with autoimmune diseases, and people with rare genetic disorders are unclear.

“We also don't know for sure whether this vaccine is safe and effective in different types of people, such as pregnant women, the elderly, or those with a chronic illness,” MedicalXpress reported. “Once a vaccine is deployed ‘in the real world,’ we'll start to understand its true effectiveness. In practice, this is likely to be different to its efficacy in highly controlled clinical trials.”

Specific disorders sometimes require avoiding certain vaccines. The CDC maintains a comprehensive list of vaccine contraindications and precautions, including a recommendation that live virus vaccines “should not be administered to severely immunocompromised persons.”

The CDC cautions that anyone with a “weakened immune system, or has a parent, brother, or sister with a history of hereditary or congenital immune system problems” should talk to their doctor before being vaccinated. People who have had any other vaccines in the past 4 weeks should also consult with a provider first.  

The American Cancer Society recommends against live vaccines for patients getting chemotherapy or radiation treatment.

“In general, anyone with a weak immune system should not get any vaccines that contain live virus. There are a few vaccines that contain live viruses, which can sometimes cause infections in people with weak immune systems that can become life-threatening,” the Society warns.

Autoimmune disorders are also complex. The Hospital for Special Surgery warns that live vaccines “are not recommended for lupus patients, due to the increased risk of infection from the vaccine.”

Most vaccines are very safe for most people. But vaccine safety presents a big question for a small group of people with specific risk factors like cancer or chronic illness. At this point there is simply no safety data on COVID-19 vaccines in such people. Hopefully there will soon be clear answers.

Roger Chriss lives with Ehlers Danlos syndrome and is a proud member of the Ehlers-Danlos Society. Roger is a technical consultant in Washington state, where he specializes in mathematics and research.