3.4.1. Safety
The evidence of the safety of MAV/06 vaccines has been accumulated and demonstrated through several clinical trials and 30 years of real-world use. The secured safety data is as follows:
The safety of the MAV/06 vaccine has been confirmed through various clinical trials. When summarizing the safety results obtained from these trials, the following points emerge:
MAV/06 vaccine has demonstrated satisfactory safety profiles across different age groups, including infants, children, adolescents, and adults.
Safety assessments conducted in both healthy individuals and those with compromised immune function (such as immunocompromised infants) have shown satisfactory outcomes.
No significant differences in safety profiles were observed between MAV/06 vaccine and comparator vaccine (such as VARIVAX) in randomized controlled trials.
The vaccine exhibited satisfactory safety outcomes at different dosage levels, ranging from 300 PFU to 25,000 PFU.
Safety assessments conducted in various countries, including S.Korea, Thailand, the Philippines, and Vietnam, have consistently confirmed the safety of MAV/06 vaccine across diverse populations.
Overall, the comprehensive safety data obtained from multiple clinical trials support the conclusion that the MAV/06 vaccine is safe for use in the prevention of varicella infection (
Table 7).
- 1.
Safety and immunogenicity of live attenuated varicella vaccine (MAV/06 strain) in adults and children (1994) [
59]
In Korea, safety was confirmed by administering MAV/06 vaccines ranging from 300 PFU to 2,000 PFU to a total of 62 healthy adults and children (30 adults, 32 infants). Safety issues were not observed, and no serious adverse events were reported. Additionally, no significant adverse effects were identified.
- 2.
Immunogenicity and safety of live attenuated vaccine (MAV/06 strain) on healthy children and immunocompromised children (1995) [
60]
In Korea, safety was confirmed by administering the MAV/06 vaccine to a total of 177 healthy infants, children, and adolescents (aged 12 months to 19 years), as well as 22 immunocompromised infants (who had undergone medical treatment for conditions such as 6 leukemia, 10 solid tumors, and 6 nephrotic syndromes). No unusual adverse events were observed.
- 3.
Immunogenicity and safety of a new live attenuated varicella vaccine (MAV/06 strain) among healthy Filipino children of ages 9 months to 17 years (2001) [
61]
In the Philippines, the MAV/06 vaccine was administered to a total of 375 healthy infants and children (aged 9 months to 17 years). Safety was assessed by dividing the participants into age-specific groups, and the vaccine was well tolerated with no serious or unusual adverse events were reported.
- 4.
A single-center, dose block-randomized, single-blind, active-controlled, dose-escalation phase I clinical trial to evaluate the safety and efficacy of MG1111 in healthy adults (2015) [
62,
63]
In Korea, a total of 39 healthy adults were recruited, with the WHO pre-qualified vaccine VARIVAX serving as the control vaccine. The BARYCELA inj. vaccine was administered at different doses (2,000 PFU, 8,000 PFU, 25,000 PFU) to assess safety. No significant safety issue was observed in the overall trends and no serious adverse event was reported (ClinicalTrials.gov ID; NCT02367638).
- 5.
A Phase II, single-blind, randomized, multi-center, active-controlled, dose-escalation study to evaluate safety and efficacy of MG1111 in healthy children (2017) [
64,
65]
In Thailand, a total of 299 healthy infants and children (aged 12 months to 12 years) were recruited. The WHO pre-qualified vaccine VARIVAX served as the control vaccine. The BARYCELA inj. vaccine was administered at different doses (2,000 PFU, 8,000 PFU, 25,000 PFU) to assess safety. Vaccination with all groups was safe and well-tolerated in subjects aged 12 months to 12 years (ClinicalTrials.gov ID; NCT03375502).
- 6.
Immunogenicity and safety profiles of a new MAV/06 strain varicella vaccine in healthy children: A multinational, multicenter, randomized, double-blinded, active-controlled phase III study (2018) [
64,
65,
66]
In both Korea and Thailand, a total of 515 healthy infants and children (aged 12 months to 12 years) were recruited. The WHO pre-qualified vaccine VARIVAX served as the control vaccine. The subjects were randomly assigned in a 1:1 ratio, with 258 subjects receiving BARYCELA and 257 subjects receiving VARIVAX. Safety was assessed, and it was confirmed that there were no significant differences compared to the control group (ClinicalTrials.gov ID; NCT03375502).
- 7.
An open-label, bridging study to assess the safety and immunogenicity of BARYCELA inj. in healthy Vietnamese children aged between 12 months to 12 years (2024) [
67,
68]
In Vietnam, a total of 250 healthy infants and children were vaccinated with BARYCELA vaccine. Safety was assessed by dividing the participants into age-specific groups, and safety findings continue to support good safety profile in healthy children aged 12 months to 12 years. Satisfactory safety was confirmed in all groups (ClinicalTrials.gov ID; NCT05664152).
Once a medicine receives regulatory approval and is marketed, periodic benefit-risk evaluation reports (PBRER), previously known as Periodic Safety Update Reports (PSUR), are prepared according to the ICH E2C (R2) guideline [
69].
As of March 2024, four reports have been compiled for Varicella Vaccine-GCC inj., while six reports have been prepared for BARYCELA inj. These reports include information on the quantities of vaccines supplied during a specific period and adverse reaction cases reported in the field during that period.
Varicella Vaccine-GCC inj. was distributed a total of 29,224,770 doses from 2005 to June 2022. Among these, there were 120 reports about adverse drug reactions. BARYCELA inj. has been distributed 528,360 doses since 2020 and 3 voluntary adverse reaction reports have been accumulated [
44,
46,
55,
70,
71,
72,
73,
74,
75,
76] (
Table 8).
Table 8.
Summary of PBRER(PSUR) for Varicella Vaccine-GCC inj. and BARYCELA inj. [
44,
46,
55,
70,
71,
72,
73,
74,
75,
76].
Table 8.
Summary of PBRER(PSUR) for Varicella Vaccine-GCC inj. and BARYCELA inj. [
44,
46,
55,
70,
71,
72,
73,
74,
75,
76].
Vaccine |
Report version |
Reporting Period |
Distribution (vials) |
Overall reported ADRs1 cases |
Conclusion |
Varicella Vaccine-GCC inj. |
PSUR v1.0 |
January 2005-June 2013 |
6,512,915 |
3 |
There were no new safety issues associated with Varicella Vaccine-GCC inj. during this PSUR reporting period |
PSUR v2.1 |
June 2013- June 2016 |
5,070,608 |
30 |
There were no new safety issues associated with Varicella Vaccine-GCC inj. during this PSUR reporting period |
PBRER v3.0 |
June 2016-June 2019 |
11,475,897 |
77 |
No new relevant safety findings which would necessitate an analysis and a change in the current reference safety information |
PBRER v4.0 |
June 2019-June 2022 |
6,165,350 |
10 |
No new relevant safety findings which would necessitate an analysis and a change in the current reference safety information |
Total |
29,224,770 |
120 |
- |
BARYCELA inj. |
PBRER v1.0 |
March 2020-September 2020 |
- * |
- |
No new relevant safety findings which would necessitate an analysis and a change in the current reference safety information |
PBRER v2.0 |
September 2020 -March 2021 |
- * |
- |
No new relevant safety findings which would necessitate an analysis and a change in the current reference safety information |
PBRER v3.0 |
March 2021-September 2021 |
- * |
- |
No new relevant safety findings which would necessitate an analysis and a change in the current reference safety information |
PBRER v4.0 |
September 2021 -March 2022 |
52,070 |
- |
No new relevant safety findings which would necessitate an analysis and a change in the current reference safety information |
PBRER v5.0 |
March 2022-March 2023 |
182,980 |
1 |
No new relevant safety findings which would necessitate an analysis and a change in the current reference safety information |
PBRER v6.0 |
March 2023-March 2024 |
293,310 |
2 |
No new relevant safety findings which would necessitate an analysis and a change in the current reference safety information |
Total |
528,360 |
3 |
- |
Although direct comparison may be limited due to differences in pharmacovigilance reporting systems among manufacturers and countries, as well as variations in reporting practices across nations, it can be observed that MAV/06 vaccine demonstrates a lower incidence of adverse reactions compared to other varicella vaccines. This suggests favorable safety outcomes post-market approval (
Table 9) [
77,
78,
79].
Some countries have incorporated a two-dose regimen of varicella vaccine into their NIP, and the WHO also recommends a two-dose vaccination to further reduce the incidence of varicella cases and to decrease outbreaks in the community [
6].
In line with this, a study was conducted to assess the safety of cross-vaccination with MAV/06 and vOka-derived vaccines when administered in a two-dose regimen [
80].
The study involved a total of 406 Korean infants, who received the first and second doses of vaccination with MAV/06-vOka, vOka-MAV/06, MAV/06-MAV/06 and vOka-vOka, respectively. The study confirmed that there were no safety concerns associated with this cross-strain vaccination regimen.
Antibiotics (e.g., Kanamycin, Neomycin, and Erythromycin) are generally used to prevent contamination of cells during a manufacturing process of vaccines. There are possibilities that these antibiotics may cause adverse drug reactions such as anaphylaxis in some people after administration [
81]. However, BARYCELA inj. is a varicella vaccine that does not contain antibiotics, thus eliminating the risk of adverse reactions associated with antibiotics [
47,
49,
50,
51].
3.4.2. Immunogenicity
The gold standard test for measuring VZV antibodies is the Fluorescent Antibody to Membrane Antigen (FAMA) assay, developed in the 1970s. Additionally, the glycoprotein enzyme-linked immunosorbent assay (gpELISA) is commonly used. Generally, an FAMA antibody titer of 1:4 or higher is considered seropositive, indicating protection against varicella [
5,
82,
83].
The immunogenicity of MAV/06 vaccines have been investigated tested through several clinical trials and studies.
Through various clinical trials, high post-vaccination antibody titers and very high seroconversion rates (SCRs) have been confirmed.
In South Korea, the SCR of MAV/06 vaccines (BARYCELA inj. and Varicella Vaccine-GCC inj.) were close to 100% in healthy infants and children aged 12 months to 19 years, and immunocompromised children.
In the Philippines, healthy infants and children aged 9 months to 17 years, the SCR of Varicella Vaccine-GCC inj. was close to 100% at both 6 weeks and 5 years after vaccination.
In Thailand, the SCR of BARYCELA inj. was close to 100% in healthy infants and children aged 12 months to 12 years.
In Vietnam, healthy infants and children, high antibody titers of 69.9 and 126.5 were observed after vaccination with BARYCELA inj. (
Table 10).
Safety and immunogenicity of live attenuated varicella vaccine (MAV/06 strain) in children (1994) [
59]
In South Korea, a total of 32 healthy children with negative FAMA antibodies before vaccination were vaccinated with MAV/06 vaccine doses ranging from 300 PFU to 1,000 PFU to confirm immunogenicity. The results showed that regardless of the vaccine dose, children had a 100% SCR and high antibody levels 4 weeks after vaccination.
- 2.
Immunogenicity and safety of live attenuated vaccine (MAV/06 strain) on healthy children and immunocompromised children (1995) [
60]
In South Korea, a total of 161 healthy children and adolescents (aged 12 months to 19 years) and 18 immunocompromised children (who had undergone medical treatment for conditions such as 6 leukemia, 10 solid tumors, and 6 nephrotic syndromes) were vaccinated with MAV/06 vaccine to confirm immunogenicity. After 4 weeks, both healthy children and immunocompromised children showed a 100% SCR.
- 3.
Immunogenicity and safety of a new live attenuated varicella vaccine (MAV/06 strain) among healthy Filipino children of ages 9 months to 17 years (2001) [
61]
In the Philippines, a total of 299 healthy infants and children (aged 9 months to 17 years) were vaccinated with MAV/06 vaccine, and immunogenicity was assessed by age group. The average SCR was confirmed to be 99.7% six weeks after vaccination.
- 4.
A 5-year follow-up immunogenicity of a new live attenuated varicella vaccine (MAV/06 strain) among healthy Filipino children of ages 9 months to 17 years (2006) [
74,
84]
In 2001, a clinical study was conducted in the Philippines to assess the immunogenicity and safety of the vaccine [
61]. Five years later, long-term immunogenicity and protective efficacy were evaluated. Among the 299 healthy children enrolled in the study, 163 were followed up, and 162 of them were confirmed to be seropositive (99.4%).
- 5.
A single-center, dose block-randomized, single-blind, active-controlled, dose-escalation phase I clinical trial to evaluate the safety and efficacy of MG1111 in healthy adults (2015) [
62,
63]
In a study conducted in Korea, a total of 39 healthy adults were vaccinated with BARYCELA inj. at different doses (2,000 PFU, 8,000 PFU, 25,000 PFU) with WHO pre-qualified vaccine VARIVAX as the control vaccine. After 6 weeks, the FAMA GMT results for each dose were found to be 78.8, 90.5, and 68.6, respectively (ClinicalTrials.gov ID; NCT02367638).
- 6.
A Phase II, single-blind, randomized, multi-center, active-controlled, dose-escalation study to evaluate immunogenicity and safety of MG1111 in healthy children (2017) [
64,
65]
In a study conducted in Thailand, a total of 193 healthy infants and children (12 months to 12 years) were vaccinated with BARYCELA inj. at different doses (2,000 PFU, 8,000 PFU, 25,000 PFU) with WHO pre-qualified vaccine VARIVAX as the control vaccine. After 6 weeks, the results showed a 100% SCR for each dose, with geometric mean titer (GMT) results of 85.5, 109.9, and 65.6, respectively (ClinicalTrials.gov ID; NCT03375502).
- 7.
Immunogenicity and safety profiles of a new MAV/06 strain varicella vaccine in healthy children: A multinational, multicenter, randomized, double-blinded, active-controlled phase III study (2018) [
64,
65,
66]
In both Korea and Thailand, a total of 478 healthy infants and children (aged 12 months to 12 years) were enrolled in a randomized, 1:1 controlled trial, with WHO pre-qualified vaccine VARIVAX as the control vaccine and BARYCELA as the test vaccine (239 subjects in each group). After 6 weeks, the test group showed non-inferiority compared to the control group in terms of immunogenicity. The SCR results were 97.9% and 99.2% for the test and control groups, respectively. The GMT results were 74.2 and 112.7, respectively (ClinicalTrials.gov ID; NCT03375502).
- 8.
An open-label, bridging study to assess the safety and immunogenicity of BARYCELA inj. in healthy Vietnamese children aged between 12 months to 12 years (2024) [
67,
68]
In Vietnam, a total of 246 healthy infants and children were vaccinated with the BARYCELA vaccine. They were divided into age-specific groups to assess immunogenicity. After 6 weeks, the GMT results for each age group were 69.9 and 126.5, respectively (ClinicalTrials.gov ID; NCT05664152).
In 2016, a study conducted in South Korea examined the seropositivity rate among total 715 children who received the varicella vaccines distributed in Korea. In the study, the seropositivity of the MAV/06 vaccine using the FAMA test was 74%, while the seropositivity of a vOka derived vaccine (Vari-L) was 63% [
85]. This result is similar to the findings from previous studies conducted in the United States in 2006 (76%) [
5,
86] and in Korea in 2010 (83.6%) [
82] (
Table 11).
Furthermore, in a Korean study [
85], there was a tendency that antibody levels (assessed with gpELISA tests) decreased as age of children increased from 1 to 4 years. However, there was no significant difference in the tendency between the MAV/06 vaccine group and the Oka vaccine group, indicating a long-term persistence of antibodies of the MAV/06 vaccines would be similar to that of the Oka vaccine [
85].
CMI is known to play a crucial role in regulating VZV and providing protection against additional VZV infections. Therefore, it was investigated whether CMI is induced after MAV/06 vaccination using a non-clinical animal model, and the results confirmed the induction of CMI through a Th1 cell-mediated response [
87].
VZV exhibits genetic variation regionally, but currently licensed varicella vaccines are all developed based on clade 2 strains [
4,
7,
88]. Studies have investigated whether antibodies generated from Oka varicella vaccines elicit immune responses against different genotypes of varicella viruses [
89]. Similarly, research has been conducted to assess cross-reactivity of antibodies generated after MAV/06 vaccination with varicella viruses of different clades, using both animal and human sera [
87,
90]. The findings indicate that antibodies generated after MAV/06 vaccination show effective immune responses against varicella viruses of different clades (clade 1, 3, and 5), including wild-type clade 2 viruses, demonstrating high and similar FAMA antibody titers across different clades [
90].