Recommendations for Adult Pneumococcal Vaccination in Korea: 2026 Update Incorporating the 21-Valent Pneumococcal Conjugate Vaccine

Abstract

The 21-valent pneumococcal conjugate vaccine (PCV21; CAPVAXIVE; Merck Sharp & Dohme) is the first pneumococcal conjugate vaccine (PCV) specifically designed for adults, targeting serotypes that currently cause disease in this population. PCV21 includes 11 serotypes not contained in any other approved PCV (9N, 15A, 15C, 16F, 17F, 20A, 23A, 23B, 24F, 31, and 35B), together with serotypes 3, 6A, 7F, 8, 10A, 11A, 12F, 19A, 22F, and 33F. PCV21 was approved by the Korean Ministry of Food and Drug Safety in August 27, 2025. The Adult Immunization Committee of the Korean Society of Infectious Diseases recommends one of the following options for all adults aged ≥65 years and for adults aged 19–64 years at increased risk of pneumococcal disease: a single dose of PCV21, a single dose of PCV20, or sequential PCV15 followed by PPSV23, with no stated preference among these options. When PCV21 or PCV20 is administered, no additional pneumococcal vaccination is required. Because PCV21 does not include serotype 4, in populations with a high incidence of serotype 4 disease, PCV20 alone or sequential PCV15 followed by PPSV23 may be preferentially considered.

Summary of Recommendations

• 1. All adults aged ≥65 years and adults aged 19–64 years at increased risk (those with chronic medical conditions, cerebrospinal fluid leak or cochlear implant, immunocompromising conditions, and functional or anatomical asplenia) should receive one of the following:

  • ① A single dose of 21-valent pneumococcal conjugate vaccine (PCV21);
  • ② A single dose of 20-valent pneumococcal conjugate vaccine (PCV20); or
  • ③ 15-valent pneumococcal conjugate vaccine (PCV15) followed by 23-valent pneumococcal polysaccharide vaccine (PPSV23) in sequence.

• 2. The choice of vaccine, dosing intervals, and schedule according to underlying conditions and prior vaccination history are summarized in Table 2.

Background

The 21-valent pneumococcal conjugate vaccine (PCV21; CAPVAXIVE; Merck Sharp & Dohme, Rahway, NJ, USA) is the first pneumococcal conjugate vaccine (PCV) reformulated around the serotypes responsible for the predominant burden of pneumococcal disease in adults. PCV21 excludes the serotypes whose incidence has declined as an indirect effect of pediatric PCV programs (1, 4, 5, 6B, 9V, 14, 18C, 19F, and 23F) and includes eight unique serotypes that are not contained in any other approved vaccine (15A, 15C, 16F, 23A, 23B, 24F, 31, and 35B), together with serotypes 3 and 19A, which are among the most frequent causes of adult pneumococcal disease (Table 1). Each serotype is conjugated to a CRM¹⁹⁷ carrier protein. Although PCV21 does not directly include serotype 15B, cross-reactive immune responses with serotype 15C have been demonstrated. Accordingly, the vaccine has been approved for the prevention of invasive pneumococcal disease (IPD) caused by a total of 22 serotypes (3, 6A, 7F, 8, 9N, 10A, 11A, 12F, 15A, 15B, 15C, 16F, 17F, 19A, 20A, 22F, 23A, 23B, 24F, 31, 33F, and 35B) [1]. PCV21 was approved by the Korean Ministry of Food and Drug Safety on August 27, 2025, following its approval by the United States (US) Food and Drug Administration in June 2024 [1,2]. The indication for the prevention of non-invasive pneumococcal pneumonia with PCV21 is based on serotypes directly included in the vaccine (excluding serotype 15B) [1]. Among currently available pneumococcal vaccines, PCV21 provides the broadest serotype coverage. In PCV-experienced adults, its complementarity with previously administered vaccines may further expand cumulative serotype coverage. In clinical trials, PCV21 demonstrated non-inferior immune responses compared with the 20-valent pneumococcal conjugate vaccine (PCV20; Prevnar20; Pfizer, New York, NY, USA) for shared serotypes and superior opsonophagocytic activity (OPA) titers for its unique serotypes. Cost-effectiveness analyses in the United States and Canada have suggested that PCV21 is cost-effective relative to PCV20 and to sequential vaccination with the 15-valent pneumococcal conjugate vaccine (PCV15; VAXNEUVANCE; Merck Sharp & Dohme, LLC) followed by the 23-valent pneumococcal polysaccharide vaccine (PPSV23) [3,4,5]. However, because PCV21 does not include serotype 4, in settings where serotype 4 disease is prevalent, a single dose of PCV20 or sequential PCV15 followed by PPSV23 may be preferentially considered over PCV21, as these strategies may provide broader serotype coverage [6].

Table 1. Serotypes contained in approved pneumococcal vaccines^a,b .

Vaccine	1	3	4	5	6A	6B	7F	9V	14	18C	19A	19F	23F	22F	33F	8	10A	11A	12F	15B	2	9N	17F	20	15A	15C	16F	23A	23B	24F	31	35B
PCV13
PCV15
PCV20
PCV21
PPSV23

^aThe PCV21 indication for serotype 15B is based on cross-reactivity with serotype 15C.

^bPCV21 contains serotype 20A. The component listed as “serotype 20” in the approved PPSV23 formulation is, in fact, the serotype 20A polysaccharide.

PCV13, 13-valent pneumococcal conjugate vaccine; PCV15, 15-valent pneumococcal conjugate vaccine; PCV20, 20-valent pneumococcal conjugate vaccine; PCV21, 21-valent pneumococcal conjugate vaccine; PPSV23, 23-valent pneumococcal polysaccharide vaccine.

Recommendations

The Adult Immunization Committee of the Korean Society of Infectious Diseases recommends that all adults aged ≥65 years and adults aged 19–64 years at increased risk of pneumococcal disease receive one of the following options: a single dose of PCV21, a single dose of PCV20, or sequential PCV15–PPSV23 (Table 2). All three options have been approved and recommended on the basis of immunogenicity (OPA titer) data rather than clinical efficacy data. Because it is uncertain whether differences in immunogenicity translate directly into differences in real-world clinical protection, the three options are recommended equally, without preference. The three vaccination strategies (PCV21, PCV20, and sequential PCV15–PPSV23) have distinct advantages and disadvantages with respect to serotype composition, vaccination schedule, and immunological mechanism (Table 3). PCV21 is intended primarily for adult use and does not include serotype 4. In populations with a high incidence of serotype 4 pneumococcal diseases, PCV20 alone or sequential PCV15 followed by PPSV23 may be preferentially considered over PCV21.

Table 2. Recommendations by age, prior vaccination history, and underlying conditions.

Risk group or age	Prior vaccination history	Recommendation
Adults aged ≥65 years	Unvaccinated or PCV7 only	A single dose of PCV21, PCV20, or PCV15. If PCV15 is used, give PPSV23 ≥1 year later (a minimum interval of 8 weeks may be used in adults with immunocompromising conditions*, cochlear implants, or cerebrospinal fluid leaks).
	PPSV23 only	A single dose of PCV21, PCV20, or PCV15 ≥1 year after the most recent PPSV23.
	PCV13 only	A single dose of PCV21 or PCV20 ≥1 year after PCV13.
	PCV13–PPSV23 (completed before age 65)	A single dose of PCV21 or PCV20 ≥5 years after the most recent pneumococcal vaccine.
	PCV13–PPSV23 (completed at age ≥65)	Shared clinical decision-making is recommended for additional PCV21 or PCV20 in adults aged ≥65 years who have completed both PCV13 and PPSV23. If administered, give a single dose ≥5 years after the most recent vaccine.
Adults aged 19–64 years with immunocompromising conditionsa, cerebrospinal fluid leak, or cochlear implant	Unvaccinated or PCV7 only	A single dose of PCV21, PCV20, or PCV15. If PCV15 is used, give PPSV23 ≥8 weeks later.
	PPSV23 only	A single dose of PCV21, PCV20, or PCV15 ≥1 year after the most recent PPSV23.
	PCV13 only	A single dose of PCV21 or PCV20 ≥1 year after PCV13.
	PCV13–one dose of PPSV23	A single dose of PCV21 or PCV20 ≥5 years after the most recent pneumococcal vaccine. The series is then complete and no further doses are needed.
	PCV13–two doses of PPSV23	Reassess recommendations at age 65. Alternatively, a single dose of PCV21 or PCV20 may be given ≥5 years after the most recent vaccine to complete the series.
Adults aged 19–64 years with chronic medical conditionsb	Unvaccinated or PCV7 only	A single dose of PCV21, PCV20, or PCV15. If PCV15 is used, give PPSV23 ≥1 year later.
	PPSV23 only	A single dose of PCV21, PCV20, or PCV15 ≥1 year after the most recent PPSV23.
	PCV13 only	A single dose of PCV21 or PCV20 ≥1 year after PCV13.
	PCV13–one dose of PPSV23	Reassess recommendations at age 65.

^aImmunocompromising conditions: chronic kidney failure, nephrotic syndrome, congenital or acquired immunodeficiency, iatrogenic immunosuppression, generalized malignancy, HIV infection, Hodgkin disease, leukemia, lymphoma, multiple myeloma, solid organ transplantation, congenital or acquired asplenia, sickle cell disease, and other hemoglobinopathies.

^bChronic medical conditions: alcohol use disorder, chronic cardiovascular disease (including heart failure and cardiomyopathy), chronic liver disease, chronic lung disease (including chronic obstructive pulmonary disease, emphysema, and asthma), cigarette smoking, and diabetes mellitus.

PCV7, 7-valent pneumococcal conjugate vaccine; PCV21, 21-valent pneumococcal conjugate vaccine; PCV20, 20-valent pneumococcal conjugate vaccine; PCV15, 15-valent pneumococcal conjugate vaccine; PPSV23, 23-valent pneumococcal polysaccharide vaccine; PCV13, 13-valent pneumococcal conjugate vaccine.

Note: PPSV23 is no longer recommended as an option for completing the pneumococcal vaccine series in adults with prior PCV13 vaccination; the series should be completed with a single dose of PCV21 or PCV20. In adults who have received PCV15, a single subsequent dose of PPSV23 completes the sequential vaccination series. If PPSV23 cannot be obtained in adults who have received PCV15 but have not yet completed the series, a single dose of PCV21 or PCV20 may be substituted.

Table 3. Comparison of single-dose PCV21, single-dose PCV20, and sequential PCV15–PPSV23 vaccination strategies.

Comparison	Single-dose PCV21	Single-dose PCV20	Sequential PCV15–PPSV23
Serotype coverage	22 serotypes (8 unique) including the cross-reactive serotype 15B; broadest overall serotype coverage, particularly advantageous for adults previously vaccinated. Does not include serotype 4; PCV20 or sequential PCV15 followed by PPSV23 may be preferred in settings where serotype 4 disease is prevalent.	20 serotypes	24 serotypes
Schedule	Single dose; simple	Single dose; simple	Two doses; complex schedule
Immunogenicity	Non-inferior to PCV20 for shared serotypes and superior immunogenicity for unique serotypes	Non-inferior to PCV13–PPSV23	PCV15 demonstrated superior immunogenicity to PCV13 for serotype 3 and non-inferior immunogenicity for 22F and 33F
Safety	Comparable to other conjugate vaccines	Comparable to other conjugate vaccines	Comparable to PCV13–PPSV23
Indicated age	Adults ≥18 years (primarily targeted at adults)	All ages from 6 weeks of age	PCV15: ≥6 weeks; PPSV23: ≥2 years
Approval in the Korea	27-Aug-25	31-Oct-24	PCV15: October 31, 2023; PPSV23: previously approved

PCV21, 21-valent pneumococcal conjugate vaccine; PCV20, 20-valent pneumococcal conjugate vaccine; PCV15, 15-valent pneumococcal conjugate vaccine; PPSV23, 23-valent pneumococcal polysaccharide vaccine; PCV13, 13-valent pneumococcal conjugate vaccine.

Epidemiology

The indirect effects of pediatric pneumococcal conjugate vaccination on adults grow as pediatric coverage increases and accumulate progressively over time, reaching an approximately 90% reduction in vaccine-serotype IPD over roughly nine years after program initiation [7]. As the indirect effects of pediatric PCV vaccination increase, the relative serotype coverage provided by PCV21 becomes broader. According to US Centers for Disease Control and Prevention data from 2018 to 2022, serotypes included in PCV21 accounted for approximately 85% of IPD cases among adults aged ≥65 years, compared with approximately 54% for PCV20 [8]. Pneumococcal pneumonia accounts for 12–13% of all hospitalizations for pneumonia in the US, and epidemiological modeling estimates approximately 225,000 adult hospitalizations per year [9]. Active surveillance studies before the coronavirus disease 2019 pandemic reported approximately 30,000 cases of IPD and approximately 100,000 hospitalizations for non-invasive pneumococcal pneumonia annually among US adults [6]. The incidence of IPD is higher among older adults and individuals with underlying risk factors, and the case-fatality rate exceeds 10%. Substantial racial disparities in pneumococcal disease persist in the US In 2018, active bacterial core surveillance (ABCs) data showed all-age IPD incidence rates of 13.2 per 100,000 in Black persons and 9.1 per 100,000 in White persons [10]. Following the introduction of PCV13 in children, the disparity in PCV13-serotype IPD among adults narrowed through indirect effects; however, residual disparities have been largely driven by non-PCV13 serotypes. Incidence rates of non-PCV13 serotype disease were notably higher in American Indian/Alaska Native adults (25 per 100,000) and Black adults (10 per 100,000) compared with the overall population average of 6 per 100,000 [6].

According to ABCs data from 2018–2019, serotypes included in PCV13, PCV15, PCV20, and PPSV23 accounted for 27%, 42%, 54%, and 62%, respectively, of IPD cases in adults aged ≥65 years; serotype 3 accounted for 62% of PCV13 serotype IPD in 2018, making it the most prevalent PCV13 serotype [11]. Between 2018 and 2022, PCV21 serotypes accounted for approximately 80% of IPD cases among vaccine-eligible adults, of which 20–30% were attributable to the eight serotypes unique to PCV21 [6]. Serotype 4, which is not included in PCV21, declined markedly following the introduction of pediatric PCV7 but has recently re-emerged in parts of the western US, including Alaska, the Navajo Nation, Colorado, New Mexico, and Oregon. This re-emergence has occurred predominantly among adults younger than 65 years with risk factors such as substance use disorders or homelessness. In these settings, PCVs that include serotype 4, such as PCV20 or PCV15 followed by PPSV23, may be preferentially considered over PCV21 [6]. When serotype 4 accounts for ≥30% of pneumococcal disease, PCV20 is expected to provide broader serotype coverage than PCV21 and to be more cost-effective.

In 2022, the incidence and mortality rates of IPD among adults aged 50–64 years were 13.2 and 1.8 per 100,000, respectively, representing the highest rates after those observed in adults aged ≥65 years [9]. Approximately 90% of patients aged 50–64 years hospitalized with IPD or pneumococcal pneumonia had at least one risk factor. Although 32–54% of adults in this age group were eligible for risk-based pneumococcal vaccination, the actual vaccination coverage was only 37%, considerably lower than the 70% coverage observed in adults aged ≥65 years; racial disparities in vaccination coverage were also evident [9]. According to ABCs data from 2018–2022, PCV20 and PCV21 serotypes accounted for 56% and 83%, respectively, of IPD cases in adults aged 50–64 years; including serotype 15B raised the proportion attributable to PCV21 serotypes to 85% [9]. In Black adults, IPD incidence reached its peak earlier (at 55–59 years) than in non-Black adults, highlighting a pronounced racial disparity in this age group. Considering this epidemiological evidence, the limited effectiveness of risk-based vaccination strategies, and racial health disparities, the US Advisory Committee on Immunization Practices (ACIP) expanded the universal recommendation for pneumococcal vaccination from age ≥65 years to age ≥50 years, in October 2024 [9].

In Korea, the national immunization program (NIP) has supported pneumococcal conjugate vaccination in children since 2013 (with approximately 97% coverage in 2023) and PPSV23 vaccination in adults aged ≥65 years (with cumulative coverage of 78.5% as of 2020) [12,13,14]. Despite this, IPD and pneumococcal community-acquired pneumonia continue to impose a substantial disease burden, predominantly affecting older adults and high-risk groups. In 2024, 451 cases of IPD were notified in Korea, of which 64.5% occurred in adults aged ≥60 years [15]. The overall case-fatality in 2024 was 19.3%, and approximately 90% of deaths occurred in adults aged ≥60 years, indicating that the burden is concentrated in older age groups [15]. In serotype distributions of adult IPD between 2019 and 2021, the proportions of cases caused by serotypes contained in approved vaccines were 31.9% for PCV13, 36.2% for PCV15, 50.9% for PCV20, 56.0% for PPSV23, and 62.9% for PCV21; non-vaccine serotypes accounted for 25% [16]. Notably, serotypes 3 and 19A continue to account for the largest share of adult IPD in Korea [16]. In contrast to the recent re-emergence of serotype 4 in parts of the US, serotype 4 was not detected in this nationwide adult IPD surveillance [16]. Therefore, the recommendation to preferentially consider serotype 4-containing vaccines, such as PCV20 or sequential PCV15 followed by PPSV23, in settings with a high incidence of serotype 4 disease is not currently applicable in Korea. Nevertheless, continued national serotype surveillance remains essential to detect any future emergence of serotype 4 and to inform timely adjustments to adult pneumococcal vaccination strategies.

Evidence from clinical trials

The STRIDE clinical trial program evaluated PCV21 across a broad spectrum of adult populations for pneumococcal vaccination, including healthy adults, older adults across prespecified age strata of 50–64, 65–74, 75–84, and ≥85 years, pneumococcal vaccine–naïve and vaccine-experienced individuals, adults with chronic medical conditions, and those with immunocompromising conditions such as HIV infection [17,18,19,20]. PCV21 elicited consistently robust immune responses with a comparable safety profile across these subgroups, with no clinically meaningful differences by age, prior vaccination status, or underlying condition. Korean clinical sites participated in the international STRIDE-3, STRIDE-6, and STRIDE-8 trials, supporting the generalizability of these findings to Korean adults [17,18,19]. In addition, concomitant administration of PCV21 with quadrivalent inactivated influenza vaccine was evaluated in STRIDE-5, a phase 3, randomized, double-blind, placebo-controlled trial in adults aged ≥50 years [21]. Co-administration elicited immune responses to PCV21 serotypes and influenza strains that were generally non-inferior to those observed with sequential administration, with a comparable safety and tolerability profile. These findings support the co-administration of PCV21 with seasonal influenza vaccine in routine adult immunization practice.

Position on the age threshold and simplification of the vaccination strategy

Adult pneumococcal vaccination strategies have changed substantially in recent years, driven by three converging factors: the introduction of higher-valent conjugate vaccines, shifts in serotype epidemiology, and the limited effectiveness of risk-based vaccination strategies. In October 2024, the US ACIP comprehensively revised its adult pneumococcal vaccination recommendations, recommending PCV21, PCV20, or sequential PCV15–PPSV23 with no stated preference [9]. When PCV21 or PCV20 has been administered, no additional pneumococcal vaccination is required. In addition, PPSV23 is no longer recommended as an option for completing the vaccination series in adults who previously received PCV13; instead, the series should be completed with PCV21 or PCV20. The age threshold for universal recommendation was lowered from ≥65 years to ≥50 years, reflecting the substantial disease burden in adults aged 50–64 years and the limited effectiveness of risk-based vaccination strategies, which have been associated with low vaccination coverage in practice [9].

In Korea, the age-based pneumococcal vaccination recommendation is maintained at ≥65 years, reflecting the persistently high disease burden among older adults. Expansion to adults aged 50–64 years requires a cautious approach because the supporting evidence remains limited. The rationale for retaining the age threshold at ≥65 years is as follows. First, although IPD is reported through the national mandatory communicable disease surveillance system, the annual number of notified cases was only 451 in 2024, which is substantially smaller than that captured by the US ABCs system and is insufficient to support expansion of universal vaccination based on disease burden in adults aged 50–64 years. Second, systematic epidemiological data on IPD incidence stratified by age and risk factors in Korean adults aged 50–64 years are not yet available. Third, serotype distribution data for this age group are also limited and do not provide a sufficient basis for expanding the recommendation. Fourth, the lack of such data makes it difficult to conduct separate cost-effectiveness analyses for the 50–64-year age group. As Korean epidemiological evidence and cost-effectiveness data accumulate, expansion of the age-based universal recommendation should be reconsidered. Finally, the current structure of the Korean NIP should also be taken into account. The NIP currently provides a single dose of PPSV23 to adults aged ≥65 years, whereas PCVs have not yet been incorporated into the national program for older adults. Therefore, establishing the role of higher-valent PCVs within the existing ≥65-year NIP, together with evaluations of their effectiveness, cost-effectiveness, reimbursement, and programmatic feasibility, should be considered a higher priority than expanding routine age-based vaccination to adults aged 50–64 years. Future expansion of the age-based recommendation should ideally be considered after these issues have been addressed and sufficient epidemiological evidence has become available.

In its 2024 recommendations, the National Advisory Committee on Immunization (NACI) of Canada articulated the core principle that all eligible adults should receive at least one dose of either PCV20 or PCV21 [22]. Specifically, NACI recommends a single dose of PCV20 or PCV21 for older adults aged ≥65 years and for high-risk adults aged <65 years, regardless of prior pneumococcal vaccination history (including PCV13, PCV15, or PPSV23). For adults previously vaccinated with PPSV23 or any PCV, an interval of at least one year from the most recent dose is recommended; in immunocompromised adults, this interval may be shortened to a minimum of 8 weeks. This recommendation offers the practical advantage of simplifying the vaccination schedule. In contrast, sequential administration of PCV15 followed by PPSV23 requires complex decision-making regarding dosing intervals, which may range from 8 weeks to 1 year, as well as consideration of prior vaccination history and underlying conditions. This complexity increases the decision-making burden on clinicians and may reduce completion of the PPSV23 component. The NACI approach, which emphasizes a single dose of PCV20 or PCV21 regardless of prior vaccination history, reduces this complexity, lowers administrative burden, and may improve vaccine uptake. However, because these simplified recommendations are based on Canadian serotype distribution, epidemiology, and cost-effectiveness data, their direct application to Korea requires careful evaluation in the context of the local serotype distribution, the current NIP structure, and domestic cost-effectiveness analyses.

Hematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT) recipients

HSCT recipients lose pre-existing immunity during the transplantation process; therefore, a new pneumococcal vaccination series should be initiated regardless of prior vaccination history [23]. Immune responses to the PPSV23 after HSCT are suboptimal, and graft-versus-host disease and corticosteroid therapy may further attenuate these responses. Accordingly, the primary series is initiated with a, which elicits a more reliable immune response, typically beginning at 3 months after transplantation. The series consists of three primary doses administered at 1-month intervals, followed by a booster dose 6–12 months after the third dose. The exact timing should be individualized in consultation with the transplant physician. The 10 serotypes unique to PCV20 (1, 4, 5, 6B, 9V, 14, 15B, 18C, 19F, and 23F) and the 11 serotypes unique to PCV21 (9N, 15A, 15C, 16F, 17F, 20A, 23A, 23B, 24F, 31, and 35B) are largely complementary; therefore, use of both vaccines within a single series may broaden overall serotype coverage. It is recommended that the booster dose consist of the vaccine not used in the primary series, resulting in either PCV20 × 3 followed by PCV21 × 1 or PCV21 × 3 followed by PCV20 × 1 (Table 4). However, data on the immunogenicity and safety of PCV21, either alone or in combination with PCV20, in HSCT recipients remain limited. These recommendations are therefore based on expert opinion and extrapolation from experience with other PCVs [23]. On 27 July 2026, the Korean NIP expanded pneumococcal vaccine support for HSCT recipients from children aged ≤12 years to recipients of all ages, providing financial support for a four-dose PCV20 series. Although the NIP covers the four-dose PCV20 schedule, recipients are also informed that the final booster dose may be replaced with PCV21 at their own expense to broaden serotype coverage [24].

Table 4. Pneumococcal vaccination schedule for hematopoietic stem cell transplant recipients.

Population	Primary series (3 doses)	Booster (1 dose)
Adults aged ≥19 years	PCV20 × 3 doses	PCV21 × 1 dose
Option A	4-week intervals; starting at least 3 months after transplantation	6–12 months after the third dose of the primary series
Adults aged ≥19 years	PCV21 × 3 doses	PCV20 × 1 dose
Option B	4-week intervals; starting at least 3 months after transplantation	6–12 months after the third dose of the primary series

PCV20, 20-valent pneumococcal conjugate vaccine; PCV21, 21-valent pneumococcal conjugate vaccine; PPSV23, 23-valent pneumococcal polysaccharide vaccine.

Note: Direct evidence on the immunogenicity and safety of PCV21, either alone or in combination with PCV20, in Hematopoietic stem cell transplant (HSCT) recipients is currently lacking. Accordingly, the schedules presented in this table are extrapolated from evidence on other pneumococcal conjugate vaccines and are supported by expert opinion. The same rationale applies to completing a series initiated with PCV15 and administering a booster dose with PCV20 or PCV21 to broaden cumulative serotype coverage. Korean national immunization program (NIP) support for HSCT recipients was expanded on 27 July 2026 from children aged ≤12 years to all ages, providing four doses of PCV20, which has already been supported under the pediatric NIP.

SOT recipients are at increased risk of IPD because of immunosuppressive therapy, and pneumococcal vaccination is therefore essential. Whenever feasible, the recommended pneumococcal vaccination series should be completed before transplantation, including a single dose of PCV20 or PCV21, or sequential PCV15 followed by PPSV23. However, even when pre-transplant vaccination has been completed, post-transplant immunity should not be considered sufficient. After transplantation, immune status and vaccination history should be reassessed to determine the need for additional doses. In recipients who were unvaccinated or incompletely vaccinated before transplantation, vaccination should be initiated according to the recommended post-transplant schedule. Vaccination should begin in clinically stable patients, typically 3–6 months after transplantation, using either a single dose of PCV20 or PCV21, or sequential PCV15 followed by PPSV23. In recipients who have already received PPSV23, a PCV such as PCV20 or PCV21 may be administered after an interval of at least 1 year. The timing and schedule should be individualized based on the transplanted organ, the intensity of immunosuppression, the presence of rejection, and the overall clinical condition.