• Clinical and Experimental Vaccine Research
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• v.12 no.2
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• pp.116-120
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• 2023

Purpose: In Japan, the data on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody titers after the booster dose of the coronavirus disease 2019 (COVID-19) vaccine are insufficient. The aim of this study is to evaluate changes in SARS-CoV-2 antibody titers before, 1, 3, and 6 months after the booster dose of the BNT162b2 COVID-19 vaccine among health care workers. Materials and Methods: A total of 268 participants who received the booster dose of the BNT162b2 vaccine were analyzed. SARS-CoV-2 antibody titers were measured before (baseline) and at 1, 3, and 6 months after the booster dose. Factors associated with changes in SARS-CoV-2 antibody titers at 1, 3, and 6 months were analyzed. Cutoff values at baseline were calculated to prevent infection of the omicron variant of COVID-19. Results: The SARS-CoV-2 antibody titers at baseline, and 1, 3, and 6 months were 1,018.3 AU/mL, 21,396.5 AU/mL, 13,704.6 AU/mL, and 8,155.6 AU/mL, respectively. Factors associated with changes in SARS-CoV-2 antibody titers at 1 month were age and SARS-CoV-2 antibody titers at baseline, whereas changes in SARS-CoV-2 antibody titers at 3 and 6 months were associated with the SARS-CoV-2 antibody titers at 1 month. The cutoff values of the SARS-CoV-2 antibody titers at baseline were 515.4 AU/mL and 13,602.7 AU/mL at baseline and 1 month after the booster dose, respectively. Conclusion: This study showed that SARS-CoV-2 antibody titers increase rapidly at 1 month after the booster dose of the BNT162b2 vaccine and begin to decrease from 1 to 6 months. Hence, another booster may be needed as soon as possible to prevent infection.

• Clinical and Experimental Vaccine Research
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• v.12 no.4
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• pp.337-345
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• 2023

Purpose: The global fight against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has led to widespread vaccination efforts, yet the optimal dosing schedule for SARS-CoV-2 vaccines remains a subject of ongoing research. This study aims to investigate the effectiveness of administering two booster doses as the third and fourth doses at different intervals to enhance vaccine protection. Materials and Methods: This study was conducted at a military regional hospital operated by the Ministry of National Defense in Taiwan. A cohort of vaccinated individuals was selected, and their vaccine potency was assessed at various time intervals following their initial vaccine administration. The study participants received booster doses as the third and fourth doses, with differing time intervals between them. The study monitored neutralizing antibody titers and other relevant parameters to assess vaccine efficacy. Results: Our findings revealed that the potency of the SARS-CoV-2 vaccine exhibited a significant decline 80 days after the initial vaccine administration. However, a longer interval of 175 days between booster injections resulted in significantly higher neutralizing antibody titers. The individuals who received the extended interval boosters exhibited a more robust immune response, suggesting that a vaccine schedule with a 175-day interval between injections may provide superior protection against SARS-CoV-2. Conclusion: This study underscores the importance of optimizing vaccine booster dosing schedules to maximize protection against SARS-CoV-2. The results indicate that a longer interval of 175 days between the third and fourth doses of the vaccine can significantly enhance the neutralizing antibody response, potentially offering improved protection against the virus. These findings have important implications for vaccine distribution and administration strategies in the ongoing battle against the SARS-CoV-2 pandemic. Further research and largescale trials are needed to confirm and extend these findings for broader public health implications.

• Clinical and Experimental Vaccine Research
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• v.12 no.1
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• pp.82-84
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• 2023

There were growing reports of herpes zoster reactivation after the coronavirus disease 2019 (COVID-19) vaccination, including a more severe form, herpes zoster ophthalmicus (HZO). A 35-year-old male presented HZO in his left V1 dermatome 10 days after his COVID-19 vaccine booster with Moderna (messenger RNA-1273). He had no history of chronic disease, immunocompromised, autoimmune, malignancy, or long-term immunosuppressive drug use. The rash improved without any further complications after being treated with oral valacyclovir for 7 days. This was a unique case of HZO after the COVID-19 vaccine in a booster setting in healthy younger adults. The association of herpes zoster after a COVID vaccine remained inconclusive and potentially coincidental, especially without the known risk factor. However, we would like to add a report to increase awareness among physicians and the general population, for early recognition and treatment with an antiviral.

• Clinical and Experimental Vaccine Research
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• v.13 no.1
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• pp.35-41
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• 2024

Purpose: The effectiveness of coronavirus disease 2019 (COVID-19) vaccination schemes and the combination of vaccines of various platforms for administering booster doses is still being studied since it will depend on the population's response to vaccines. We aimed to evaluate the safety, protection, and immunogenicity of the Salvadorean population's third dose booster COVID-19 vaccine and the potential benefit of homologous vs. heterologous regimens. Materials and Methods: This is an analytical observational cohort study in a population aged 18 to 65 years that was primarily vaccinated with AstraZeneca, Sinovac, or Pfizer/BioNTech. Volunteers were recruited (n=223) and followed up for 3 months after receiving the 3rd vaccine (BNT162b2) as a booster. Adverse reactions were monitored, serum anti-spike immunoglobulin G (IgG) was assessed by chemiluminescence, and a polymerase chain reaction was carried out when subjects developed clinical signs. Results: The cohorts finally included 199 participants, and we observed only mild adverse effects in all cohorts. A significant increase in specific IgG levels was found after the booster dose in all cohorts. The heterologous scheme with Sinovac showed the greatest increase in antibody titer, and a decrease was observed in all participants after 3 months. During the follow-up period, 30 participants showed symptomatology compatible with COVID-19, but only four were laboratory-confirmed and they showed mild clinical signs. Conclusion: These findings indicate that the booster doses used were safe and promoted an immediate increase in immunogenicity, which decreased over time. The heterologous regimen showed stronger immunogenicity compared to the messenger RNA-based homologous scheme.

• Journal of Preventive Medicine and Public Health
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• v.20 no.2 s.22
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• pp.280-286
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• 1987

For evaluating the boosting (anamnestic) effects of the most recent commercially produced plasma derived heat-inactivated hepatitis B vaccine (A. Co.), 117 adults with naturally acquired antibody to hepatitis B surface antigen (anti-HBs) were selected at random. In addition, out of case immunized at zero and 1 month, and boosted at 6 months (primary boosting) by conventional vaccine (B. Co), inactivated by pepsin digestion and formalin treatment, 11 cases who showed elevated titer after primary boosting were also submitted to the study. The results were as follows: 1) Out of the 117 subjects with naturally acquired anti-HBs, 6(5.1%) showed isolated anti-HBs and the titers were below 10 ratio units (RU). Negative seroconversion was seen in 4(3.4%) of the 117 cases at 12 months after the screening and, of these cases, 3 showed isolated anti-HBs and the titers were below 10 RU. 2) Eighty-three percent of the cases with naturally acquired isolated anti-HBs below 10 RU did not respond to a booster injection with 3 us dose of A. Co. vaccine at all, but 90% of the other subjects responded. 3) The anti-HBs titers of all the 11 cases who showed a rise of more than 10 RU (increased GMT, 28.04) at one month after primary booster injection by $20{\mu}g$ dose of B. Co. vaccine decreased at 19 months after the primary booster. And 3 subjects (27.3%) of the 11 reached negative seroconversion. All of the 11 cases, who had secondary booster injection with $3{\mu}g$ dose of A. Co. vaccine at 19 months after primary boosting, showed increased anti-HBs titer at least 20 RU or more (increased GMT, 57. 72) at one month after the boosting. According to the above results in the anti-HBs screening survey for the purpose of immunization with hepatitis B vaccine, subjects with isolated anti-HBs below 10 RU should be regarded as being in an unimmunized state. In cases who are in risk circumstances, immunized primarily with a $20{\mu}g$ dose of B. Co. vaccine, a secondary booster injection should be given within 2 years after initiation of primary immunization and a $3{\mu}g$ booster dose of A. Co. vaccine can be reliably used.

• Journal of Microbiology and Biotechnology
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• v.28 no.1
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• pp.136-144
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• 2018

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis. Bacillus Calmette-$Gu\acute{e}rin$ (BCG) vaccine is the only TB vaccine currently available, but it is not sufficiently effective in preventing active pulmonary TB or adult infection. With the purpose of developing an improved vaccine against TB that can overcome the limitations of the current BCG vaccine, we investigated whether adjuvant formulations containing de-O-acylated lipooligosaccharide (dLOS) are capable of enhancing the immunogenicity and protective efficacy of TB subunit vaccines. The results revealed that the dLOS/dimethyl dioctadecyl ammonium bromide (DDA) adjuvant formulation significantly increased both humoral and Th1-type cellular responses to TB subunit vaccine that are composed of three antigens, Ag85A, ESAT-6, and HspX. The adjuvanted TB vaccine also effectively induced the Th1-type response in a BCG-primed mouse model, suggesting a potential as a booster vaccine. Finally, the dLOS/DDA-adjuvanted TB vaccine showed protective efficacy against M. tuberculosis infection in vitro and in vivo. These data indicate that the dLOS/DDA adjuvant enhances the Th1-type immunity and protective efficacy of the TB subunit vaccine, suggesting that it would be a promising adjuvant candidate for the development of a booster vaccine.

• Pediatric Infection and Vaccine
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• v.5 no.1
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• pp.67-68
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• 1998

• Clinical and Experimental Pediatrics
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• v.54 no.4
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• pp.163-168
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• 2011

Purpose: The purpose of this study was to evaluate the immune response to serotype 19A in children aged 12-23 months after immunization of the 19F containing 7-valent pneumococcal conjugate vaccine (PCV7). Methods: Blood samples from a total of 45 subjects (age 12-23 months) were included in the study. Subjects were categorized according to immunization status into three groups as follows: 18 subjects with 3 primary doses and 1 booster dose of PCV7 (booster group), 21 subjects with 3 primary doses before 12 months of age (primary group), and 6 subjects with no vaccination history of PCV7 (control group). An ELISA and opsonophagocytic killing assay (OPKA) was done to evaluate the immune responses against serotypes 19F and 19A. Results: According to the ELISA, all subjects had antibody titers ${\geq}0.35{\mu}g/mL$ for serotypes 19F and 19A in the booster and primary group and 83.0% and 66.7% in the control group, respectively. According to the OPKA, subjects with opsonic activity (${\geq}20$) against serotypes 19F and 19A were 100% and 61.1% of the subjects in the booster group and 66.7% and 19.0% in the primary group, respectively. No subjects in the control group had opsonic antibodies against both serotypes. Conclusion: In conclusion, in children 12-23 months age who were previously vaccinated with PCV7, a cross-reactive immune response is elicited against serotype 19A after a primary series of 3 doses in a small proportion of subjects, and this response is amplified after booster vaccination.

• Clinical and Experimental Pediatrics
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• v.51 no.6
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• pp.622-628
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• 2008

Purpose : The purpose of this study was to evaluate the immunogenicity of the booster immunization with pneumococcal conjugate vaccine in Korean children. Methods : Thirty-nine children aged 12-23 months who visited Kangnam CHA Hospital between September 2006 and December 2006 were enrolled. The children were divided into primary and booster groups depending on their vaccination status for the 7-valent pneumococcal conjugate vaccine. The anti-pneumococcal antibody levels of each serotype included in the vaccine (4, 6B, 9V, 14, 18C, 19F, 23F) were determined by third-generation ELISA. Results : The geometric mean titer (GMT) of antibodies to each pneumococcal serotype in the booster group was higher than in the primary group (P<.05). The percentage of subjects with pneumococcal antibodies ${\geq}0.35{\mu}g/mL$ was 90.5-100% for all serotypes in both the primary and booster groups. The percentage of subjects with pneumococcal antibodies ${\geq}1.0g/mL$ in the booster group was 94.4-100%, which was higher than the primary group except for serotypes 6B and 14 (P<.05). The percentage of subjects with pneumococcal antibodies ${\geq}5.0{\mu}g/mL$ in the booster group was 50.0-94.4% which was higher than the primary group for all serotypes (P<0.05). Conclusion : The immunogenicity of a booster dose of the pneumococcal conjugate vaccine in Korean children was high and the immunogenicity of a primary series was also relatively high. To determine the feasibility of the introduction of the pneumococcal conjugate vaccine and the appropriate schedule for Korean children, further prospective investigation of the immunogenicity of the booster immunization is needed.

• The Journal of Korean Society of Virology
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• v.30 no.1
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• pp.11-18
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• 2000

Since $Hantavax^{TM}$, formalin inactivated Hantaan virus vaccine (10,240 ELISA units/ml), has been developed in 1990 to prevent against haemorrhagic fever with renal syndrome (HFRS) caused by Hantaan or Seoul virus, it has been commercially available in Korea. Twenty-one healthy people were booster shot once and twice after primary basic vaccination with $Hantavax^{TM}$. Seroconversion rates were measured by immunofluorescent antibody technique (IFAT), enzyme-linked immunosorbent assay (ELISA), high density composite particle agglutination (HDPA), and plaque reduction neutralization test (PRNT). Seroconversion rates of 21 vaccinees at one year after primary basic vaccination were 52.3%, 95.2%, 0.0%, 47.6%, and 28.6%, and 13 vaccinees at one month after 1st booster vaccination were 100%, 100%, 30.7%, 100% and 100% by IFAT, ELISA (IgG, IgM), HDPA and PRNT, respectively. Seroconversion rates declined slightly by twenty months, and they were 84.6%, 92.3%, 0.0%, 84.6% and 69.2% by IFAT, ELISA (IgG, IgM), HDPA and PRNT, respectively. Seroconversion rates of 9 vaccinees at three months after 2nd booster vaccination were 100%, 100%, 0.0%, 100%, and 88.9%, and 16 vaccinees at one year after the 2nd booster vaccination were 87.5%, 93.8%, 0.0%, 87.5% and 81.3% by IFAT, ELISA (IgG, IgM), HDPA and PRNT, respectively. Based on the above result $Hantavax^{TM}$ has proved a vigorous anamnestic response after the 1st and the 2nd booster vaccination and has persisted higher fluorescence, agglutination and neutralizing antibody titers in vaccinees.