Immunogenicity and safety of co-immunization of children with live attenuated varicella-zoster virus vaccine and live attenuated hepatitis A virus vaccine
Objective 
To investigate the immunogenicity and safety of co-immunization of children with live attenuated varicella-zoster virus (VZV) vaccine and live attenuated hepatitis A virus (HAV) vaccine. 
 
 
Methods 
A total of 686 children aged 18-24 months were recruited in Henan province of China and divided into three groups. Children in the three groups were respectively immunized with live attenuated VZV vaccine or live attenuated HAV vaccine alone or in combination. Blood samples were collected from all subjects before and one month after vaccination for the detection of seroconversion and seropositive rates. Occurrence of adverse events was monitored for safety evaluation. Antibody membrane immune-fluorescence assay and enzyme immunoassay were performed to detect the antibodies against VZV and HAV, respectively. 
 
 
Results 
The seroconversion rates of anti-VZV antibody were both 100% in children received co-immunization or VZV vaccine immunization alone. The geometric mean titer (GMT) of anti-VZV antibody in co-immunization group was higher than that of VZV vaccine immunization group (P<0.001). The GMT and seroconversion rate of anti-HAV antibody in children immunized with live attenuated VZV vaccine and live attenuated HAV vaccine were similar to those immunized with live attenuated HAV vaccine alone (P=0.94, P=0.77). Adverse reactions were reported in 156 subjects with a rate of 22.74%, mainly manifested as fever and swelling. No other adverse reactions were observed. No significant differences in the adverse events were observed between the three groups. 
 
 
Conclusion 
Co-immunization children with live attenuated varicella vaccine and live attenuated hepatitis A virus vaccine provided equivalent immunogenicity and safety in comparison with immunization the two vaccines alone, indicating the feasibility of co-immunization strategy. 
 
 
Key words: 
Live attenuated varicella vaccine; Live attenuated hepatitis A virus vaccine; Co-immunization; Immunogenicity; Safety