Immune Response to COVID-19 Vaccines

We have shared both our clinical experience and studies that demonstrate clinical effectiveness and safety of COVID-19 vaccines in people with Down syndrome. However, until recently, studies have not been available that demonstrate the immune response. Two recent articles reported on research on the immune response to COVID-19 immunization in people with Down syndrome. Both articles demonstrated good antibody response to the COVID vaccine in people with Down syndrome. Our takeaways from the studies are shared below. More detailed information about each study can be found at the end of this article.

Key Takeaways

In both studies, the immune systems of the individuals with Down syndrome responded positively to COVID-19 vaccination. 

• In both studies, an increase was found in the blood tests of immune function of people with Down syndrome. This indicates the immune response was activated against COVID-19 (as desired) from the vaccine.

• The study by Valenti et al. (see below) noted that the immune response of individuals with Down syndrome was lower than individuals without Down syndrome 7 days after the second dose of the Pfizer-BioNTech vaccine series. The clinical implications of this finding were not discussed. However, as mentioned above, our experience at the Adult Down Syndrome Center and other studies have found people with Down syndrome who received COVID-19 vaccination are less likely to contract COVID-19 or to experience serious illness from COVID-19 than people with Down syndrome who did not receive COVID-19 vaccination. This suggests that the immune response, even if it is lower in people with Down syndrome, is still beneficial.

• The study by Esparcia-Pinedo et al. (see below) found that the immune response of individuals with Down syndrome over 40 years of age was lower than individuals under 40 years of age. People with Down syndrome over age 40 are more at risk for serious illness from COVID-19 infection. We think it is particularly important that people with Down syndrome over 40 years of age (who do not have a contraindication) receive COVID-19 vaccination and use additional caution to limit/avoid exposure to COVID-19.

Based on what we know about COVID-19 infection and vaccination in individuals with Down syndrome, we recommend the following:

• People with Down syndrome who do not have a contraindication should receive COVID-19 vaccination, both the initial series and the booster shot. It is particularly important because many people with Down syndrome are at greater risk for serious illness from COVID-19 infection.

• We are following the CDC recommendations for booster doses. We are not presently recommending an additional booster (e.g., a 4th dose of Pfizer or Moderna) for people with Down syndrome unless they are 50 years of age or older or they have other health conditions that would cause greater immune system dysfunction (as identified by the CDC ). Despite demonstration of some relative immune impairment in some people with Down syndrome, Down syndrome by itself is not included in the CDC’s “moderately to severely immunocompromised" category.

Articles

Safety and Long-Term Immunogenicity of BNT162b2 Vaccine in Individuals with Down Syndrome 

In this study, Valenti et al (2022) investigated the antibody response to the COVID-19 vaccine (BioNTech, Pfizer) in individuals with Down syndrome in Italy.

• They reported an antibody response 21 days after the first dose that was comparable to those without Down syndrome.

• At day 21, the second dose was given. Seven days after the second dose was given (28 days after the first dose), a good antibody response was also noted but it was not as high as those without Down syndrome.

• At 180 days, both the individuals with and without Down syndrome showed decline in their antibody response. 

The side effects were reported as mild. The authors concluded that the data demonstrate a good safety and immunogenicity (immune response) profile of the vaccine. They also concluded that the data reinforce current national and international vaccine recommendations against COVID-19, including providing one booster shot.

Development of an Effective Immune Response in Adults with Down Syndrome after SARS-CoV-2 Vaccination 

In the second study, available in pre-print form, Esparcia-Pinedo et al (2022) reported a measurable immune response of both the humoral (antibody) and cellular (T cells) parts of the immune systems of individuals with Down syndrome in Spain. The response was measured at 1 and 3 months after the 2-shot series of the COVID-19 vaccine. Some participants received a mRNA vaccine, and some received a vaccine using different technology (such as the adenovirus-based vaccines). The findings included:

• The T-cells continued to rise at 6 months (an indicator of a good “cellular” immune response).

• At 6 months, they did note a decrease in the antibodies to COVID-19. Despite the decrease, there was still an effective immune response after six months in 98% of individuals with Down syndrome.

• Compared to individuals younger than age 40, individuals with Down syndrome over age 40 had a lower level of antibody response at 1-3 months as well as a lower persistent antibody level at 6 months.

To see all our resources on COVID-19, please visit this link.