Study Shows Immune Cells Against Covid-19 Stay High in Number Six Months After Vaccination

A recent study by Johns Hopkins Medicine researchers provides evidence that CD4+ T lymphocytes — immune system cells also known as helper T cells — produced by people who received either of the two available messenger RNA (mRNA) vaccines for COVID-19 persist six months after vaccination at only slightly reduced levels from two weeks after vaccination and are at significantly higher levels than for those who are unvaccinated.

The researchers also found that the T cells they studied recognize and help protect against the delta variant of SARS-CoV-2, the virus that causes COVID-19. According to the U.S. Centers for Disease Control and Prevention, the delta variant — currently the predominant strain of SARS-CoV-2 in the United States — causes more infections and spreads faster than earlier forms of the virus.

The study findings were first reported online Oct. 25, 2021, in the journal Clinical Infectious Diseases.

“Previous research has suggested that humoral immune response — where the immune system circulates virus-neutralizing antibodies — can drop off at six months after vaccination, whereas our study indicates that cellular immunity — where the immune system directly attacks infected cells — remains strong,” says study senior author Joel Blankson, M.D., Ph.D., professor of medicine at the Johns Hopkins University School of Medicine. “The persistence of these vaccine-elicited T cells, along with the fact that they’re active against the delta variant, has important implications for guiding COVID vaccine development and determining the need for COVID boosters in the future.”

To reach these findings, Blankson and his colleagues obtained blood from 15 study participants (10 men and five women) at three times: prior to vaccination, between seven and14 days after their second Pfizer/BioNTech or Moderna vaccine dose, and six months after vaccination. The median age of the participants was 41 and none had evidence of prior SARS-CoV-2 infection.

CD4+ T lymphocytes get their nickname of helper T cells because they assist another type of immune system cell, the B lymphocyte (B cell), to respond to surface proteins — antigens — on viruses such as SARS-CoV-2. Activated by the CD4+ T cells, immature B cells become either plasma cells that produce antibodies to mark infected cells for disposal from the body or memory cells that “remember” the antigen’s biochemical structure for a faster response to future infections. Therefore, a CD4+ T cell response can serve as a measure of how well the immune system responds to a vaccine and yields humoral immunity.

In their study, Blankson and colleagues found that the number of helper T cells recognizing SARS-CoV-2 spike proteins was extremely low prior to vaccination — with a median of 2.7 spot-forming units (SFUs, the level of which is a measure of T cell frequency) per million peripheral blood mononuclear cells (PBMCs, identified as any blood cell with a round nucleus, including lymphocytes). Between 7 and 14 days after vaccination, the T cell frequency rose to a median of 237 SFUs per million PBMCs. At six months after vaccination, the level dropped slightly to a median of 122 SFUs per million PBMCs — a T cell frequency still significantly higher than before vaccination.

The researchers also looked six months after vaccination at the ability of CD4+ T cells to recognize spike proteins atop the SARS-CoV-2 delta variant. They discovered the number of T cells recognizing the delta variant spike protein was not significantly different from that of T cells attuned to the original virus strain’s protein.

Although the study was limited because of the small number of participants, Blankson feels it pinpoints areas that merit further research.

“The robust expansion of T cells in response to stimulation with spike proteins is certainly indicated, supporting the need for more study to show booster shots do successfully increase the frequency of SARS-CoV-2-specific T cells circulating in the blood,” says Blankson. “The added bonus is finding that this response also is likely strong for the delta variant.”

Along with Blankson, the members of the study team from Johns Hopkins Medicine are study lead author Bezawit Woldemeskel and Caroline Garliss.

This study was supported by the Johns Hopkins COVID-19 Vaccine-related Research Fund.

The authors do not have financial or conflict of interest disclosures. 

New Analysis: More U.S. Adults Identify as Disabled; Ethnic and Socioeconomic Disparities Persist

A new analysis led by Johns Hopkins Medicine researchers finds that the number of U.S. adults who report they have a disability is 27%, representing 67 million adults, an increase of 1% since the data were last analyzed in 2016. In this new study, which used data collected in 2019, before the COVID-19 pandemic, the researchers found a wide array of disparities between socioeconomic and demographic factors that persists among those who identify as disabled and those who do not.

“To reduce ableism and create more inclusive communities, our country must be equipped with data on the prevalence of disabilities and who is most impacted by them,” says Bonnielin Swenor, Ph.D., M.P.H., director of the Johns Hopkins Disability Health Research Center and associate professor of ophthalmology at the Johns Hopkins University School of Medicine and Wilmer Eye Institute.

Swenor and her research team analyzed survey data from the Centers for Disease Control and Prevention’s 2019 Behavioral Risk Factor Surveillance System, a collection of health and behavior information from annual telephone surveys of more than 400,000 U.S. adults.

Results of the analysis were published Oct. 21 in JAMA Network Open.

Approximately 27% of American adults reported a disability. When compared with the U.S. adult population, this represents 67 million adults. An additional 6 million people reported a disability since data on disability prevalence were analyzed and reported in 2016.

In the current study, approximately 12% of American adults reported more than one disability. Mobility was the most often reported disability type, followed by cognitive/mental, independent living (requiring help for daily tasks and outings), hearing, vision, and self-care (needing help with bathing, dressing and other personal care tasks).

In addition, the researchers analyzed socioeconomic and demographic data to better understand the prevalence of disability across intersecting groups.

“Developing effective measures and policies to include people with disabilities in all aspects of life needs to account for the variability in how people among different ethnic, socioeconomic, demographic and geographic groups experience disability,” says Swenor. “With robust data, we can strengthen the foundation of our knowledge about disability and develop tangible solutions.”

The survey data showed that, compared with adults without a disability, disabled adults were more likely to be older, female, Hispanic, have less than a high school education, have low income, be unemployed, and be bisexual, transgender or gender nonconforming. Digging deeper, the team found differences in disability prevalence based on sociodemographic groups. For example, Black females had a higher prevalence of disability than females of other races, and Black adults identifying as gay or bisexual had a lower prevalence of disability compared with gay or bisexual adults of other races.

Swenor and the research team note that an aging population and other factors may contribute to the increase in reported disability. The data include information from before the COVID-19 pandemic, and Swenor says there may be an increase in people reporting a disability resulting from long-term symptoms of COVID-19.

The research team aims to use these data to continue studying the experiences of disabled populations, including identifying and finding support and resources for people with disabilities and ascertaining the capabilities of schools and employers in supporting disabled communities.

In addition to Swenor, researchers who contributed to the report include Jessica Campanile, Jennifer Deal, Ph.D., Nicholas Reed, Au.D., and Varshini Varadaraj, M.D., M.P.H.

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