We don’t yet know how effective COVID vaccines are for people with immune deficiencies.

What are immunodeficiencies?

Immunodeficiencies are conditions that weaken the body’s ability to fight infection. People’s immune system may be compromised for many reasons, and this can be transient or lifelong.

Primary immunodeficiencies occur when some or all of a person’s immune system is missing, defective or ineffective. These are rare and often genetic diseases that may be diagnosed early in life, but can occur at any age.

Examples of primary immunodeficiencies include severe combined immunodeficiency (SCID) and common variable immunodeficiency (CVID).

Secondary immunodeficiencies are acquired, and more common. They may occur as a result of other diseases (for example, via HIV infection), treatments and medications (such as chemotherapy or corticosteroids), or environmental exposure to toxins (for example, prolonged exposure to heavy metals or pesticides).

Sometimes the immune system in people with immunodeficiencies can react in exaggerated ways too, and cause autoimmune disease (such as rheumatoid arthritis or gut inflammation). So it sometimes makes more sense to describe the immune system as “dysregulated”, rather than “deficient”.

Immunodeficiencies, COVID-19 and vaccines

People with secondary immunodeficiencies are generally at higher risk of becoming infected with SARS-CoV-2 and of developing severe disease. Surprisingly, although people with primary immunodeficiency may be at greater risk of getting infections, including COVID, most are no more susceptible to developing severe COVID compared with the overall population.

This may be because the most severe COVID-19 symptoms are usually not due to gaps in immunity, but to an overactive immune response to SARS-CoV-2.

In fact, immune-suppressing steroids may be an effective treatment for severe COVID. Clinical trials looking into this are underway.

However, as vaccines work by mobilising our immune systems, for people who have a weaker immune system to begin with, vaccines may not be as effective. They may generate an incomplete or short-lived response, so people with immunodeficiencies may need additional boosters to maintain protective immunity.

Efficacy and safety

It’s difficult to assess COVID vaccine efficacy in people with immunodeficiencies, because people with primary immunodeficiencies or cancer weren’t included in clinical trials.

A very small number of people with HIV have been included in trials of a few of the vaccines, but limited data is publicly available. So it’s too early to draw any firm conclusions on whether the vaccines will be as effective in people with HIV as for the general population.

We also don’t yet know how long immunity to COVID-19 or COVID vaccines lasts. This will be particularly important for immunodeficient people. Research is underway to determine whether they’ll need booster jabs more frequently to maintain immunity.