to 6 weeks of a vaccination, subsequent vaccinations with either the same or different immunogens could be associated with a greater risk of GBS than if the person had never had GBS. A previous history of GBS unrelated to vaccination as an antecedent event is even more uncertain as a risk factor.

The term neuropathy as used here designates those disorders of peripheral nerves other than GBS and has, on occasion, been described in relation to vaccine administration. Most reports fall into two clinical categories, mononeuropathy and brachial neuritis. Diagnosis in both instances rests upon the clinical and electrodiagnostic features. A mononeuropathy implies dysfunction limited to the distribution of a single peripheral nerve large enough to be named. In some instances, mononeuropathy is clearly related to direct injection of vaccine into or near the nerve trunk, as with radial nerve palsy with wrist drop following a misdirected deltoid injection (Ling and Loong, 1976). Brachial neuritis is also known as brachial plexus neuropathy or, in the United Kingdom, as neuralgic amyotrophy. Brachial neuritis is frequently heralded by deep, steady aching pain in the shoulder and upper arm. The annual incidence of brachial neuritis in Rochester, Minnesota, from 1970 to 1981 was 1.64 per 100,000 people (Beghi et al., 1985). For a more complete description, see Chapter 3.

Mononeuropathies, particularly those resulting from direct injection of a substance into the nerve trunk, have been described in the literature in relation to injection of vaccines as well as other therapeutic agents (Ling and Loong, 1976). Brachial neuritis has also been linked to vaccination. A review of brachial neuritis by Tsairis and colleagues (1972) states that about 15 percent of all cases of brachial neuritis occurred following administration of vaccine or antiserum, with tetanus toxoid being the most frequently cited.

Injury of a peripheral nerve by intramuscular injection can result from the needle or injection of the solution into a nerve (Scheinberg and Allensworth, 1957). Nerve damage may also result from chemical irritation and the toxic