Transmission of Vaccine-Strain Varicella-Zoster Virus: A Systematic Review.

CONTEXT

Live vaccines usually provide robust immunity but can transmit the vaccine virus.

OBJECTIVE

To assess the characteristics of secondary transmission of the vaccine-strain varicella-zoster virus (Oka strain; vOka) on the basis of the published experience with use of live varicella and zoster vaccines.

DATA SOURCES

Systematic review of Medline, Embase, the Cochrane Library, Cumulative Index to Nursing and Allied Health Literature, and Scopus databases for articles published through 2018.

STUDY SELECTION

Articles that reported original data on vOka transmission from persons who received vaccines containing the live attenuated varicella-zoster virus.

DATA EXTRACTION

We abstracted data to describe vOka transmission by index patient's immune status, type (varicella or herpes zoster) and severity of illness, and whether transmission was laboratory confirmed.

RESULTS

Twenty articles were included. We identified 13 patients with vOka varicella after transmission from 11 immunocompetent varicella vaccine recipients. In all instances, the vaccine recipient had a rash: 6 varicella-like and 5 herpes zoster. Transmission occurred mostly to household contacts. One additional case was not considered direct transmission from a vaccine recipient, but the mechanism was uncertain. Transmission from vaccinated immunocompromised children also occurred only if the vaccine recipient developed a rash postvaccination. Secondary cases of varicella caused by vOka were mild.

LIMITATIONS

It is likely that other vOka transmission cases remain unpublished.

CONCLUSIONS

Healthy, vaccinated persons have minimal risk for transmitting vOka to contacts and only if a rash is present. Our findings support the existing recommendations for routine varicella vaccination and the guidance that persons with vaccine-related rash avoid contact with susceptible persons at high risk for severe varicella complications.