Not all virus infections produce a protective immune response in this way.

"Vaccine development or even testing should not come to a halt until we delineate what that protective immune response is," he said.

But it is also, many say, a conscious, protective response to adolescence in the United States.

During cold temperature exposure, shivering is a protective response to produce heat through muscle activity.

As a protective response, refined through the evolutionary process, it is very effective.

The take rate has been shown to closely correlate with the induction of a protective response.

However, even unicellular animals will show protective responses to, for example, extremes of temperature.

Additionally, you also have a second protective response known as the "cell-mediated immune system."

Vaccine doses from these lots are still expected to be effective in stimulating a protective response.

Not all virus infections produce a protective immune response.