Merck Discontinues Monovalent Vaccines

Merck & Co., Inc., has announced that it will not resume production of single-antigen (individual or separate) measles, mumps, or rubella vaccines. Ongoing vaccine production will instead be limited to the combination MMR vaccine. Some public health officials have expressed concerns that availability of separate measles, mumps and rubella vaccines has increased the number of at-risk children who are susceptible to one or more of these serious diseases.

Surveillance for GBS and Possible H1N1 Vaccine-Related Adverse Events

As part of nationwide safety monitoring, CDPH is identifying and reviewing adverse events potentially related to the H1N1 vaccine through two primary surveillance projects:

1) Guillain Barré Syndrome Surveillance Project
CDPH is tracking all recent cases of Guillain Barré Syndrome (GBS) in California, whether or not they have received any vaccine. Several infectious agents, including seasonal influenza infection, are believed to trigger GBS. The cause in many cases of GBS is never determined, in part because diagnostic testing is uncommon, leaving lingering uncertainty about whether immunization may have played a role.  Therefore, CDPH is performing systematic testing for known infectious causes of GBS on available clinical specimens.

CDPH learns of GBS cases from California’s neurologists, infectious disease physicians, and intensive care units and from hospital medical record reports. By mid-January 2010, 45 suspect cases of GBS had been reported. This is fewer than the number of GBS cases that would be expected to occur in recent years without H1N1 vaccination. Of these 45 patients, 18 cases met standardized GBS case definition criteria, and 6 were classified as GBS variants. Three (6%) cases had received 2009 H1N1 vaccine, and 12 (27%) had received seasonal influenza vaccine. Testing is in progress on 62 specimens from 27 patients.

To date, seasonal influenza vaccine has been associated with more GBS cases than has H1N1 vaccine.  This is consistent with immunization having a coincidental (non-causal) role. GBS occurs most often in older adults, who have had more access to seasonal than H1N1 vaccine because of H1N1 vaccine targeting policies.  Almost half of the cases of GBS in California reported to CDPH so far have begun after a recent respiratory infection (44%) such as influenza infection.

2) Non-Guillain Barré Syndrome Adverse Events Project
Adverse events that occur after receipt of the H1N1 vaccine are being reported to CDPH by California’s local health departments, clinicians, the CDPH California Encephalitis Project, and the federal Vaccine Adverse Event Reporting System (VAERS).

CDPH is reviewing patients in the following categories for additional investigation: Deaths; anaphylaxis; events during pregnancy; neurologic (other than GBS); and other (e.g., pneumonia, myocarditis, vasculitis, etc.). CDPH staff review medical records to verify diagnoses. Specimens from cases are being tested for possible infectious etiologies. To date, rates of these events occurring after receipt of H1N1 vaccine in California have not exceeded the rates expected to occur in unvaccinated persons or those receiving seasonal influenza vaccine.