"Hexaxim is Korea's first hexavalent vaccine. It is expected to play a crucial role in helping protect children's health."

Following the inclusion of Hexaxim, a hexavalent (6-in-1) DTaP vaccine, in the National Immunization Program (NIP) this year, the medical field is holding high hopes for increased convenience of immunization and improvement in vaccination rates.

The analysis is that since immunization through NIP has already been conducted, the field is already experiencing practical benefits, such as a reduced number of immunizations. It is believed that, in the long term, Hexaxim will lessen the burden of hospital visits for caretakers, alleviate the stress of infant injections, and prevent the skipping of immunizations.

Daily Pharm met with Dr. Byung Wook Eun, a professor at Nowon Eulji Medical Center, and listened to the background of the introduction of Hexaxim and its potential effects.

Hexaxim is Korea's first and only fully liquid hexavalent fully liquid formulation vaccine, preventing six diseases, including diphtheria, tetanus, pertussis (DTaP), inactivated polio vaccine (IPV), Haemophilus influenzae type b (Hib), and hepatitis B (HepB), with a single injection.

As of January 2, it has been officially introduced into the NIP, allowing the previous separate administration of the pentavalent (5-in-1) vaccine (DTaP-IPV-Hib) and the monovalent Hepatitis B vaccine to now be given in a single shot.

According to Dr. Eun, since the introduction of Hexaxim into the NIP, there has been an increase in inquiries regarding new vaccination schedules and methods in actual clinical settings.

Dr. Eun said, "With the introduction of the hexavalent vaccine, the vaccination schedule differs from the existing pentavalent vaccine, leading to many questions from both guardians and medical staff regarding vaccination criteria, interchangeability, and delayed vaccinations."

Hexaxim is already a proven vaccine overseas, having received its first approval in Europe in 2013. It is now used in over 120 countries worldwide and is recommended as a mandatory vaccination in more than 40 countries, including Europe, Canada, and Australia.

Dr. Eun explained, "The immunogenicity and safety of Hexaxim against all six infectious diseases through global clinical studies, including those conducted in Korea," and added, "In Korea, non-inferiority related to immunogenicity was confirmed through a clinical trial comparing the Hexaxim vaccination group with the group receiving the existing pentavalent DTaP combination vaccine concurrently with the monovalent Hepatitis B vaccine."

Fewer injections due to schedule changes help improve convenience

The introduction of Hexaxim has brought significant changes to the infant vaccination schedule. Previously, infants needed to receive the Hepatitis B vaccine at 0, 1, and 6 months of age and the pentavalent DTaP vaccine at 2, 4, and 6 months.

However, starting this year, the schedule has changed. After the first Hepatitis B vaccination immediately after birth, infants will now receive Hexaxim at 2, 4, and 6 months, with no additional vaccination at 1 month.

Dr. Eun stressed that "The introduction of Hexaxim reduces the total number of vaccinations by two, bringing the total to four injections." He added, "The hexavalent DTaP vaccine can administer six antigens at once, which can help improve vaccination rates compared to administering individual vaccines separately."

However, as with any new vaccine introduction, there's some initial confusion in the field. Dr. Eun explained that there have been inquiries regarding the switching to the hexavalent vaccine at 6 months if the infant has already received the pentavalent combination vaccine at 2 or 4 months.

The Korea Disease Control and Prevention Agency (KDCA) is addressing this confusion with clear guidelines. Dr. Eun stressed, "According to KDCA's official guidelines, DTaP-containing vaccines vary by manufacturer. Therefore, for the primary 3-dose series, it is recommended to administer vaccines from the same manufacturer consistently."

Dr. Eun also said, "However, since most newborns are currently starting their vaccinations with Hexaxim, inquiries about interchangeability will gradually decrease in the future," and added, "There are also questions about vaccination age and intervals. Hexaxim's recommended vaccination schedule is at 2, 4, and 6 months of age (8-week intervals), with the recommended age for the first dose being 8 weeks (2 months of age)."

However, in unavoidable circumstances, the first dose can be administered as early as 6 weeks of age. While a 2-month (8-week) interval is generally recommended, the vaccination schedule can be adjusted to a minimum of 4-week intervals. For example, if the first dose was given at 3 months of age, the second dose can be given 4 weeks later.

Dr. Eun stated, "If there are any changes to the vaccination schedule, it is crucial to consult with a healthcare professional to get guidance on the timing and vaccine selection."

There are, however, exceptional cases where Hexaxim cannot be administered. For instance, newborns born to mothers who are positive for the Hepatitis B virus must receive Hepatitis B immunoglobulin and the Hepatitis B vaccine within 12 hours of birth.

These high-risk infants also require additional Hepatitis B vaccine doses at 1, 2, and 6 months of age, thus excluding them from the Hexaxim program.

Furthermore, infants who have already completed their second Hepatitis B vaccination by 1 month of age cannot switch to Hexaxim and must continue their remaining vaccinations with the existing combination of the pentavalent vaccine and the Hepatitis B vaccine.

"Hexaxim with increased preventive effects... high hopes for increasing vaccination rates"

Dr. Eun stated that concerns about Hepatitis B antibody formation, which were previously raised by some, have been addressed through research.

In the previous schedule, Hepatitis B vaccine was administered at 0 and 1 months of age. However, with the Hexaxim schedule, the 1-month vaccination is omitted, changing the schedule to 0-2-4~6 months.

Regarding this, Dr. Eun responded, "The 0-2-4~6 month Hepatitis B vaccination schedule using Hexaxim showed immunogenicity similar to the existing 'pentavalent vaccine+Hepatitis B vaccine' schedule," and added, "Although the hexavalent vaccine includes a Hepatitis B component in addition to the existing pentavalent combination vaccine, its safety profile was confirmed to be similar to separate administrations."

One of the anticipated effects of including Hexaxim in the NIP is an improvement in vaccination rates.

Dr. Eun said, "Because a hexavalent vaccine can introduce six antigens in one shot, it can help improve vaccination rates compared to administering individual vaccines separately," and added, "Currently, infant primary vaccination rates exceed 90%, but we expect to push this figure higher with Hexaxim's introduction."

As mentioned earlier, the reduced number of vaccinations helps prevent delayed vaccinations, which in turn can lead to a higher 'right-time vaccination rate,' thereby completing vaccinations at the recommended period, thus improving overall vaccination rates.

Indeed, improvements in vaccination rates have been observed in other countries after the introduction of hexavalent combination vaccines. In Australia, after the hexavalent vaccine was included in their NIP, the vaccination rate for infants aged 12 months increased from 84.9% in 2009 to 92.6% in 2018.

Lastly, Dr. Eun added, "Misinformation about vaccines can lead to a drop in vaccination rates, and previously well-managed infectious diseases could potentially re-emerge," and urged, "We hope the public would utilize the NIP to help protect children's health."