In the United States, 3-5% of the population is immunocompromised. That may seem like a small group, but in aggregate it’s a large number of people. If you do the math (and we assume equal distribution), that means about 8 million immunocompromised people are vaccinated.

Some immunocompromised groups were included in the clinical trials. For example, in the Moderna Phase III trial, there were 176 participants with HIV/AIDS (90 in the vaccine group and 86 in the placebo group). Among the HIV/AIDS participants, 1 person got COVID19 (they were in the placebo group). Unfortunately, there were not enough people to evaluate efficacy. Other groups, like those who’ve received immunosuppressants or immune-modifying drugs within 6 months prior to screening, were purposefully excluded. So, we needed “real life” studies to show us how well they respond to the vaccine.

We are just now getting data.

Safety

The good news is the mRNA vaccine is safe among immunocompromised. For example, in a relatively large study of solid organ transplant patients, there were no serious adverse events reported, except in 1 patient with a liver transplant who developed a prickling sensation in one of their legs.

Effectiveness

The bad news is that some immunocompromised groups just don’t respond well to the vaccine. This is true after the first dose (efficacy ranging between 17-19%) and, unfortunately, after the second dose too (efficacy ranging between ranging 15-80%).

Effectiveness seems to be dependent on the type of disease. For example, a group of scientists reported that most patients with HIV seem to produce enough antibodies for protection from severe COVID19. Especially among HIV patients in the United States that are relatively healthy and being treated with retroviral drugs. Vaccines seem to also work among those with autoimmune conditions, like rheumatoid arthritis (here, here). Although the commonly used medication for RA seems to reduce efficacy (here).

But vaccines among other conditions don’t seem to work very well (or at all). Like…

Organ transplants: Overall (here and here) and, specifically, kidney transplants (here, here, here)
Dialysis (here)
Cancer: Both solid cancer (here) and blood cancer (here, here). Here is leukemia specifically
Immunosuppression overall (here)

Why isn’t the vaccine effective?

We don’t really know yet. Some scientists have hypothesized (and found) the weakened response appears to be related to certain immunosuppressive drugs. And, specifically, a commonly prescribed steroid.

There are many other unanswered questions

Other pressing questions that need to be answered are:

Does this group need a third dose?
When is it best to give the vaccine? Before or after therapy? But if you wait to get the vaccine (or to get back on medication), how long do you have to wait?

All of this is being investigated. And this is important to answer. Not only for the individuals’ sake but also for the population. Emerging evidence (case studies to be exact: here, here, and here) suggest that immunocompromised individuals act as incubator for mutations. For example, the first documented case of B.1.526 (variant first detected in New York) was found in a patient with advanced AIDS. This seems to be because some immunocompromised have prolonged viral shedding (here, here, here).

Bottom Line: Immunocompromised people that have a vaccine should behave like they aren’t vaccinated. And so should their family members and friends (and community members) around them. At least until we can get clearer evidence and more effective solutions for them.

Love, YLE

Your Local Epidemiologist

Vaccines among immunocompromised