SAN DIEGO -- A vaccine created from hepatitis B surface antigen linked to an immunostimulant led to more rapid and durable immune responses and greater seroprotection in older patients compared with the conventional vaccine, according to results of a phase III trial reported here.
SAN DIEGO, Oct. 9 -- A vaccine created from hepatitis B surface antigen linked to an immunostimulant led to more rapid and durable immune responses and greater seroprotection in older patients compared with the conventional vaccine, according to results of a phase III trial reported here.
By 28 weeks 100% of patients ages 56 to 70 had seroprotection with the investigational vaccine compared with 56% with the standard vaccine, Eduardo B. Martins, M.D., D.Phil., told attendees at the Infectious Diseases Society of America meeting.
The types and rates of adverse events were similar with either vaccine, said Dr. Martins, an employee of Dynavax Technologies in Berkeley, Calif., developer of the vaccine.
The investigational vaccine addresses a key limitation of the conventional HBV vaccine used in the United States: suboptimal response in older patients.
"Since 1990 the incidence of acute hepatitis B infection has declined by 79% in the United States," said Dr. Martins. "That decline is largely attributable to initiation of routine childhood vaccination in 1991. Hepatitis B remains a major health issue for adults."
To create the investigational vaccine, hepatitis B surface antigen (HBsAg) is combined with immunostimulatory sequence (ISS) 1018, a short DNA sequence that targets toll-like receptor 9 to enhance immune system activity.
In a phase II trial involving patients ages 40 to 70, the investigational vaccine resulted in greater serologic protection compared with the standard vaccine from week 8 through week 50, said Dr. Martins.
The phase III study involved 412 patients, ages 40 to 70, in the Philippines, Singapore, and South Korea. They were randomized to intramuscular administration of the investigational vaccine at baseline and at weeks 8 and 24 (plus placebo at week 4) or the standard vaccine at baseline and weeks 4 and 24 (plus placebo at week 8).
The primary endpoints were seroprotection (anti-HBsAg ? 10 mIU/L) four weeks after each dose and at week 50; geometric mean concentration four weeks after each dose and at week 50; and safety through week 28.
Dr. Martins reported that 97% of patients randomized to the investigational vaccine had achieved serologic protection by week 12, 99% by week 24, and 100% at weeks 28 and 50. In contrast, the conventional vaccine had achieved seroprotection in 23%, 25%, 73%, and 69% of patients at the same intervals (P