Johnson & Johnson says booster shot of its COVID-19 vaccine strengthens immunity

Johnson & Johnson said Wednesday that a second shot of its COVID-19 vaccine eight months after the initial dose was found in a study to increase people's immunity to the disease.

The drugmaker has been testing the efficacy of boosters in people who were previously injected with its single-dose vaccine. The latest findings show that individuals who received an additional shot saw a ninefold increase in antibody levels, according to J&J. The company said researchers observed a "rapid and robust" increase in antibodies in people ages 18 to 55 and in those 65 years and older who received a lower booster dose. While the company's single-shot vaccine stimulates a strong immune response, "With these new data, we also see that a booster dose of the Johnson & Johnson COVID-19 vaccine further increases antibody responses among study participants who had previously received our vaccine," said Dr. Mathai Mammen, global head of research and development at Johnson & Johnson's Janssen Pharmaceuticals, in a statement.