Newer flu vaccine as effective as traditional one

NEW YORK (Reuters Health) - A flu vaccine made through a speedier production method appears to be as safe and effective as one produced in the traditional way, a study suggests.

The conventional flu vaccine is produced using chicken eggs to grow the virus, a slow process that makes it hard to quickly boost production in response to a pandemic, such as the swine flu outbreak of 2009.

The new study looked at the effectiveness of a newer flu vaccine that is produced using dog kidney cells, rather than eggs. It is already approved in Europe under the name of Optaflu.

Such cell-culture technology is seen as a somewhat faster and more flexible means of vaccine production, and some companies, as well as public health officials, are interested in increasing its use in producing the yearly flu vaccine.

Because different strains of the flu virus circulate each flu season, vaccine makers have to alter the composition of the shot each year. Experts try to predict which strains are likely to predominate in the upcoming season, and manufacturers produce that year’s vaccine based on those recommendations.

Sometimes, as in the case of the 2009 swine flu pandemic, an unexpected strain is identified after the seasonal vaccine has been produced. A more efficient means of production could allow vaccine makers to better respond to such outbreaks.

The Optaflu vaccine was approved as a seasonal flu vaccine by the European Union in 2007, and in the U.S., Optaflu maker Novartis received nearly $500 million from the federal government to help build a North Carolina facility to produce the vaccine. Optaflu is not yet approved in the U.S., however.

For the new study, published in the journal Clinical Infectious Diseases, researchers tested the vaccine’s effectiveness among 11,400 healthy adults younger than 50 from the U.S., Finland and Poland.

Past studies of young to elderly adults had found that the Optaflu vaccine appeared safe and produced an antibody response comparable to that triggered by conventional flu vaccination. The current trial is the first to test the vaccine’s actual efficacy against infection, lead researcher Dr. Sharon Frey, of Saint Louis University Medical School, told Reuters Health.

Frey and her colleagues randomly assigned the volunteers to receive the Optaflu vaccine, a standard egg-based flu shot or a placebo shot during the 2007-2008 flu season. Both vaccines are made by Novartis, which funded the study.

Over six months, 42 Optaflu recipients -- or 1.1 percent of the group -- reported flu-like symptoms and had a flu infection confirmed by objective testing. That figure was 1.3 percent in the conventional-vaccine group and 3.6 percent in the placebo group.

Overall, the cell-based vaccine was 84 percent effective against the three flu strains included in the shot, versus the placebo; the conventional vaccine was 78 percent effective.

When it came to all circulating flu strains for the season, both vaccines, predictably, were less effective: the cell-based shot was 69 percent effective, compared with the placebo, and the conventional vaccine 63 percent.

Side effects were similar in the two vaccine groups, according to the researchers. The most common problem -- pain at the injection site -- was reported by 30 percent of Optaflu recipients, 24 percent of the egg-based vaccine group and 10 percent of the placebo group.

Between 7 percent and 15 percent of all vaccine recipients reported short-lived headaches, fatigue or muscle soreness.

The findings offer “further reassurance of the safety and efficacy” of cell-based flu vaccines, writes Dr. David Bernstein, in an editorial published with the study.

“It appears that (the vaccines) will be useful and should begin to make up part of the vaccine supply shortly,” writes Bernstein, director of the division of infectious diseases at Cincinnati Children’s Hospital.

Frey said that a cell-based flu vaccine has advantages other than more efficient production. It is safe for people with egg allergies, she noted, and it does not contain the preservative thimerosal; while a proposed link between thimerosal in vaccines and autism risk has been discredited by many studies, public concerns remain.

In his editorial, Bernstein agrees that cell-based flu vaccines would offer a number of advantages over conventional ones.

He also, however, points to some disadvantages and barriers that will have to be considered going forward -- including the general lack of experience in using the production system, the need to build expensive new manufacturing facilities, and the need for further study to ensure that cell-based flu vaccines are free of contaminants.

SOURCE: Clinical Infectious Diseases, online September 24, 2010.