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Flu vaccine grown in caterpillar cells

fall armyworm

Cells from this caterpillar, the fall armyworm, act as an incubator for the flu vaccine (Image: USDA, Douglas Ferguson)

A flu vaccine grown in caterpillar cells instead of the usual risky and uncertain method based on chicken eggs is safe and effective in people, US researchers report.

They say their findings suggest a possible short cut to making flu vaccines, focusing on a single protein in the flu virus.

Dr John Treanor of the University of Rochester in New York, who led the study, believes the vaccine may be quicker and easier to make than current vaccines.

He adds that it might also help to create a bigger supply of vaccines to fight the common seasonal flu as well as a future pandemic.

"We currently don't have enough vaccine in the US to vaccinate everybody that we would like to vaccinate," Treanor says.

"Anything that we can do to increase the vaccine supply is useful."

His team tested a vaccine called FluBl0k made by the US company Protein Sciences.

It is grown in a batch of cells taken from the fall armyworm, a kind of caterpillar.

"The company has actually taken those cells and further fooled around with them to make them better for making vaccines," Treanor says.

Writing in the Journal of the American Medical Association, Treanor and colleagues say they tested the vaccine on 460 healthy people aged 18-49 during the 2004-2005 flu season.

One-third got a smaller dose of the vaccine, one-third received a larger dose, and one-third received a placebo shot with no vaccine.

Together, the two different doses of vaccine provided 86% protection, comparable to commercially available flu shots, Treanor says.

Preventing flu

There were seven cases of flu in the group that got fake vaccines, two cases in the group that received the smaller dose, and no cases in the group that received the higher dose of vaccine.

Experts believe this so-called cell-culture method is the best way to improve the current method of making flu vaccines.


The virus must be taken from people, purified, and grown in fertilised chicken eggs. The process takes months and can easily go wrong.

Cell-culture methods can slice one or two months off the production process, Treanor says.

"Flu viruses can be temperamental, and it's not always an easy matter to get the virus to grow as you want in eggs," Treanor says.

If the next pandemic is caused by an avian flu virus such as H5N1, which kills chickens, relying on egg-based vaccines may not be a good idea.

Simpler vaccine

The FluBlOk vaccine is simpler than most current flu shots, which use pieces of the flu virus called haemagglutinin and neuraminidase.

The vaccine, which has accelerated approval status from the US Food and Drug Administration, targets only haemagglutinin.

"We got pretty good protection [against flu]," Treanor says.

The study was funded by Protein Sciences, whose researchers were co-authors of the paper.

Other companies are working on cell-culture vaccines and each one is different and proprietary, Treanor says.

Anyone who wanted to make the vaccines would have to obtain licenses from the companies that own and develop such technologies.

Tags: health, influenza, biology, biotechnology