DVIDS – News – NMR&D Commands Publish Latest Findings on COVID-19 in U.S. Sailors

SINGAPORE – Scientists from U.S. Naval Medical Research Unit (NAMRU) INDO PACIFIC, in partnership with Naval Medical Research Command (NMRC) and Walter Reed Army Institute of Research, published findings this month from a September 2023 COVID-19 study of active-duty U.S. sailors in Japan.

The goal of the study, titled “Informing the need for a SARS-CoV-2 booster based upon the immune response among young, healthy adults to variants circulating during late 2023,” was to describe the “immunologic readiness” of U.S. troops by assessing multiple components of the immune system against circulating SARS-CoV-2 (the virus that causes COVID-19) variants.

Study findings showed that the XBB.1.5-based COVID-19 booster is likely to decrease the number of duty days a Sailor might lose to infection, and that the booster could lower the risk of SARS-CoV-2 transmission, emphasizing the need for vaccination among U.S. troops.

“We hope these results can give medical providers, senior leaders, preventive medical specialists, and most importantly the individual sailor the information they need to make data-driven decisions about their health and medical readiness,” said Capt. Andrew Letizia, science director from NAMRU INDO PACIFIC.

In addition, the study found that a reduction in the antibody response for all tested variants is more pronounced in those whose last exposure to SARS-CoV-2 (either vaccine or infection) was more than 12 months prior to the participant’s enrollment, indicating a need for up-to-date vaccinations. Research has shown significant reduction in components of the immune system’s response to SARS-CoV-2, including the responses of binding and neutralizing antibodies, memory B cells and CD8+ cytotoxic T cells against circulating variants compared to non-circulating variants.

Antibodies are proteins produced by the immune system in response to an infection. By examining blood samples, researchers can detect the presence and levels of antibodies specific to SARS-CoV-2. B-cells, or B lymphocytes, are a type of white blood cell that function as part of the immune system by secreting antibodies, helping to prevent cells from becoming infected. T-cells, also known as T lymphocytes, are a type of white blood cell that play a central role in the immune response by destroying cells that have been infected with a virus, and by assisting other cells in immune response.

Addressing the long-term immunity against novel and known strains of SARS-CoV-2 in active-duty service members has been critical to researchers, as COVID-19 remains a relevant public health concern. This study focused on providing data specifically for U.S. active-duty military personnel, a community that faces a higher risk of SARS-CoV-2 infections due operating in close-quarter settings and working abroad, but in general does not suffer from severe symptoms.

“We hope this study can inform not only COVID-19 booster strategies for sailors, the fleet and the DoD overall, but young, healthy adults in general,” Letizia said. “We face growing vaccine hesitancy and misinformation that has caused a decreased vaccine uptake, especially among young adults. This is critical in the upcoming winter season when COVID-19 activity is likely to rise.”

Lt. Huy Nguyen, principal investigator for the study, emphasized that ongoing research is necessary to monitor the immunological readiness status of service members, who have become increasingly heterogenous in terms of COVID-19 exposure history.

“The SARS-CoV-2 virus continues to mutate,” Nguyen explained. “Continuous surveillance against new variants is needed to inform the need for, composition and timing of SARS-CoV-2 vaccine boosters. We plan to continue studying the immune system’s ability to identify and neutralize new variants as they emerge.”

The Naval Medical Research & Development enterprise, led by NMRC, is engaged in a broad spectrum of activity from basic science in the laboratory to field studies in austere and remote areas of the world to investigations in operational environments. In support of the Navy, Marine Corps, and joint U.S. warfighters, enterprise researchers study infectious diseases, biological warfare detection and defense, combat casualty care, environmental health concerns, aerospace and undersea medicine, medical modeling, simulation, operational mission support, epidemiology and behavioral sciences.