The Skin Factor
While some scientists and physicians studied how the body worked and how to persuade it to fend off diseases, others puzzled over how to insert medicines and other substances such as vaccines. Having an effective vaccine that could produce sufficient immunity was useless without being able to get it into the body in a harmless way. Edward Jenner used a lancet and scratched two lines on James Phipps’s arm. Fifty years after Jenner, the hypodermic syringe became available. In 1885, scientist Louis Pasteur used one to vaccinate a young boy who had been bitten by a mad dog and was sure to die of rabies—the boy lived, and immunization took another giant step forward.

As more immunizing agents became available, people saw the benefit of immunizing large groups, such as soldiers. During World War I, they were vaccinated against diphtheria; during World War II, typhus and tetanus.

The Future Has a Past
In the 19th century, use of the hypodermic syringe was limited by dependence on large needles that could rust or snap in two, glass barrels that cracked, and tips that leaked. Before disposable needles in the 1960s, needles needed to be sharpened and sterilized. Since then, technological improvements include sharper, thinner needles and safety features. Still, more than a few people would like to avoid a shot in the arm.

Hypodermic injection remains the most common method of getting through the skin. But it is not the only technology for immunization. Engineers and scientists continue to search for alternative routes into the body, such as through the moth or nose. And continuing to solve the technological problems is critical for countries in which illness and death rates are high as a result of measles, maternal tetanus, and other preventable diseases.

A successful instrument or system must get the vaccine into the body with minimal disruption, and be cost-effective for use with billions of people. And perhaps the most important problem today—preventing reuse of syringes to avoid cross-contamination—was not even imagined in the 19th century.

These devices represent different approaches to immunization. Starting upper right: reusable glass syringe and plastic case (mid-20th century); two devices currently in development (one uses microneedles and the other, intradermal injection); pre-filled single-dose injection device (2004); nasal spray device that bypasses the skin (2004); disposable safety syringe (2004); disposable plastic syringe (1990s); disposable glass syringe (1980s); air-pressure gun (1970s); glass and metal antitoxin syringe (1930s); glass window syringe and case (1880s; note the thin wires used to keep the needle barrel open); Sharps container for disposal of used needles (1990s).