Study Finds Moderna COVID-19 Vaccine Elicits Lasting Immune Response

A low dose of the COVID-19 vaccine from Moderna elicits immunity for at least 6 months, according to researchers at the La Jolla Institute for Immunology. Notably, the researchers also found no indications that vaccinated people will need a booster shot.

Although the data found that the vaccine elicited strong CD4-positive T cells, CD8-positive T cells, and antibody responses for at least 6 months after vaccination in a clinical trial, the researchers said immune responses would likely last much longer. This strong immune memory lasted in all age groups tested, including individuals over 70 years of age who are especially vulnerable to COVID-19.

“This time point is critical because that is when true immune memory has formed,” said study co-leader Daniela Weiskopf, PhD, in the press release.

Investigators compared data from recovered COVID-19 patients to vaccine trial participants who received a 25-microgram dose of the Moderna vaccine during phase 1 clinical trials. This is a quarter of the 100-microgram dose given emergency use authorization by the FDA, and although the researchers do not know whether this small dose is as effective as the larger dose, their findings showed that the T cell and antibody response is still strong.

“We wanted to see if a quarter of the dose is able to induce any immune response,” said study first author Jose Mateus Trivino, PhD, in the press release. “We had the opportunity to receive the samples from the original Moderna/[National Institutes of Health] phase 1 trial participants who had received 2 25-microgram injections of the vaccine, 28 days apart.”

According to the press release, the researchers found that the vaccine induces an adaptive immune response to the SARS-CoV-2 spike protein, which is nearly identical to the immune system’s response to a natural SARS-CoV-2 infection. The researchers added, however, that the findings do not show that a lower dose of the Moderna vaccine provides the same protection as the standard dose.

“It would take a clinical trial to tell you how protective the lower dose is,” said study co-leader Shane Crotty, PhD, in the press release.

Interestingly, however, the research did demonstrate the power of “cross-reactive” T cells. A 2020 study found that T cells in individuals who recovered from common cold coronaviruses could respond to SARS-CoV-2, although at the time researchers did not know whether this could actually protect against COVID-19.

“Understanding the role of cross-reactive T cells is important because T cells play an important role in the control and resolution of COVID-19 infections,” said study co-leader Alessandro Sette, Dr. Bio. Sci, in the press release.

In the new study, the team found that individuals with cross-reactive T cells had significantly stronger CD4-positive T cell and antibody responses to both doses of the vaccine. Sette explained that with this immune reactivity, the immune system may work faster against the virus.

The study is also one of the first to demonstrate effective CD8-positive T cell data in COVID-19 vaccine research. They found a strong CD8-positive T cell response to the low-dose Moderna vaccine, similar to the response after a patient fights a natural SARS-CoV-2 infection.

“We know naturally infected and recovered people develop excellent CD8-positive T cell responses against SARS-CoV-2; however, there was concern about the generation of CD8-positive T cells by mRNA vaccines,” Trivino said in the press release.

Future research will investigate whether the same vaccine durability holds true for other types of COVID-19 vaccines. Based on current hospitalization rates among unvaccinated individuals, Weiskopf said real-world data suggest that this immune memory does last.

REFERENCE

Moderna COVID-19 Vaccine Spurs Lasting Immune Response. News release. La Jolla Institute for Immunology; September 14, 2021. Accessed September 16, 2021. https://www.lji.org/news-events/news/post/moderna-covid-19-vaccine-spurs-lasting-immune-response/