Vaccine-Preventable Infections in Solid Organ Transplant Recipients

Vaccine-Preventable Infections in Solid Organ Transplant Recipients

In immunocompromised patients, including solid organ transplant recipients, infectious diseases are key causes of morbidity and mortality. Vaccination is a proven and efficient method of preventing communicable diseases. However, transplant recipients may be at risk for suboptimal vaccine coverage due to decreased immunogenicity of vaccines in the post-transplant setting, as well as underimmunization due to logistic complications prior to transplant, vaccine hesitancy, and imperfect financial coverage.

According to Laura N. Walti, MD, and colleagues, the actual burden of vaccine-preventable infections among recipients of solid organ transplants is unclear. The researchers conducted a cohort study designed to examine the incidence rate of vaccine-preventable infections among individuals who underwent solid organ transplant from May 2008 to June 2019 in Switzerland. Follow-up continued until December 2019. Results were reported online in JAMA Network Open.

The study exposure was solid organ transplant. The primary outcomes of interest were the incidence rate of vaccine-preventable illnesses in solid organ transplant recipients (hepatitis A and B, diphtheria, Haemophilus influenzae infection, influenza, measles, mumps, pertussis, pneumococcal disease, poliomyelitis, meningococcal disease, rubella, tetanus, tick-borne encephalitis [TBE], and varicella zoster virus [VZV] infection).

The study utilized age-adjusted standardized incidence ratios (SIRs) to examine whether vaccine-preventable infections occurred more frequently in solid organ transplant recipients compared with the general population. Factors associated with occurrence of vaccine-preventable infections among solid organ transplant recipients were explored, and associated morbidity and mortality were assessed.

The study included 4967 solid organ transplant recipients (56.0% kidney, n=2784; 22.1% liver, n=1100; 9.1% lung, n=454; 7.8% heart, n=385; and 4.9% combined, n=244) based on data from the nationwide Swiss Transplant Cohort Study (STCS). All six transplant centers in Switzerland participate in the STCS, and for the analyzed period approximately 93% of transplant recipients in Switzerland were included.

Median age of the study cohort was 54 years, 64.2% (n=3191) were male, and 35.8% (n=1776) were female. Three percent (n=151) were African, 3.7% (n=184) were Asian, 91.6% (n=4551) were White, 1.3% (n=64) were other race/ethnicity, and 2.3% (n=17) had unknown race/ethnicity.

The researchers identified 668 vaccine-preventable infections in 593 solid transplant recipients (11.9%). Most occurred more than 1 year after transplant. The most common vaccine-preventable infections were influenza (360 episodes [53.9%] in 333 patients [6.7%]), VCV (282 episodes [42.2%] in 269 patients [5.4%], and invasive pneumococcal disease (IPD; 10 episodes [1.5%] in 9 patients [0.2%]).

Noninvasive pneumococcal infections outnumbered invasive cases; this finding was similar for H influenzae. There were no cases of hepatitis A, measles, mumps, poliomyelitis, rubella, diphtheria, or tetanus identified in the solid organ transplant recipients. The incidence rate of vaccine-preventable infection was higher in recipients of a lung or heart transplant compared with recipients of a kidney or liver transplant. The incidence rate of influenza was highest in recipients of a lung transplant (40.46 [95% CI, 31.97-51.70] per 1000 person-years) and lowest in recipients of a liver transplant (8.82 [95% CI, 6.13-12.67] per 1000 person-years).

Patient characteristics associated with increased risk of occurrence of vaccine-preventable infection were age ≥65 years (incidence rate ratio [IRR], 1.29; 95% CI, 1.02-1.62) and lung or heart transplant compared with kidney transplant (lung transplant: IRR, 1.77; 95% CI, 1.38-2.26; heart transplant: IRR, 1.40; 95% CI, 1.05-1.88). There was an association between liver transplant and a decreased risk of vaccine-preventable infection (IRR, 0.62; 95% CI, 0.48-0.80) compared with kidney transplant. There was no association between the type of induction treatment and occurrence of vaccine-preventable infections.

There was no association between rejection treatment and an increased risk for vaccine-preventable infections in the following 3 months (hazard ratio, 1.26; 95% CI, 0.90-1.76). Compared with kidney transplant recipients, there was an increased risk for influenza among lung transplant recipients (IRR, 2.51; 95% CI, 1.88-3.34) and an increased risk for VZV among heart transplant recipients (IRR, 1.72; 95% CI, 1.16-2.55).

Influenza had the highest incidence rate among solid organ transplant recipients at 16.55 per 1000 person-years (95% CI, 14.86-18.46 per 1000 person-years), followed by VZV (12.83 per 1000 person-years; 95% CI, 11.40-14.44 per 1000 person-years) and IPD (0.45 per 1000 person-years; 95% CI, 0.23-0.90 per 1000 person-years).

Only data on notifiable vaccine-preventable infections were available for the general population. The overall incidence of notifiable vaccine-preventable infections was higher in the solid organ transplant population (30.57 per 1000 person-years; 95% CI, 28.24-33.10 per 1000 person-years) than in the general population (0.71 per 1000 person-years). Of the notifiable vaccine-preventable infections, the most common was influenza (0.56 per 1000 person-years), followed by IPD (0.11 per 1000 person-years) and TBE (0.02 per 1000 person-years).

SIRs were used to compare incidence rates among solid organ transplant recipients with those in the general population. Notifiable vaccine-preventable infections occurred more frequently in the solid organ transplant recipient population than in the general population (SIR, 27.84; 95% CI, 25.00-31.00). Age-adjusted incidence rates for laboratory-confirmed influenza, IPD, and invasive H influenzae were significantly higher in the solid organ transplant population. There were no significant differences between the two groups in incidence rates for invasive meningococcal disease and TBE.

The researchers cited some limitations to the findings, including the inability to provide data on pre- and post-transplant vaccination of the solid organ transplant patients, as well as the lack of detailed data on demographics other than age.

In conclusion, the authors said, “This study found that vaccine-preventable infections were common after solid organ transplant. Despite current efforts, 11.9% of recipients experienced vaccine-preventable infections. The overall incidence rate of notifiable vaccine-preventable infections in the solid organ transplant population was higher than that in the general population, including the incidence rates for influenza, IPD, and H influenzae infection. These findings suggest that efforts for optimization of vaccine strategies in solid organ transplant recipients should focus on vaccine-preventable infections with either a high incidence in this particular population or a higher incidence rate compared with the general population.”

Takeaway Points

1. Swiss researchers reported results of a nationwide cohort study designed to assess the incidence rates of vaccine-preventable infections among a population of solid organ transplant recipients.
2. Among the 4967 solid organ transplant recipients in the study, 11.9% (n=533) experienced at least one vaccine-preventable infection.
3. The overall incidence rate of notifiable vaccine-preventable infection was higher among the cohort of solid organ transplant recipients than that in the general population (30.57 per 1000 person-years vs 0.71 per 1000 person-years).

Source: JAMA Network Open