Infectious Disease Alert Updates
January 1, 2024
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By Carol A. Kemper, MD, FIDSA
Medical Director, Infection Prevention, El Camino Hospital, Palo Alto Medical Foundation
Smallpox Vaccination Effective Against Mpox
SOURCE: Titanji BK, Eick-Cost A, Partan ES, et al. Effectiveness of smallpox vaccination to prevent mpox in military personnel. N Engl J Med 2023;389:1147-1148.
An oft-asked question during the mpox syndemic of 2022 was whether previous smallpox vaccination was sufficiently protective against mpox infection. Of course, routine vaccination against smallpox vaccination in the United States ended in 1972, making those vaccine recipients older and less likely to be exposed to mpox.
In contrast, many former and a few current military personnel continue to receive smallpox vaccination as part of their duties or deployment. From 2002-2017, more than 2.6 million military personnel received smallpox vaccination with either Dryvax (a first-generation smallpox vaccine) or ACAM2000 (a second-generation smallpox vaccine), or Jynneos vaccine. This provided an opportunity for these authors to perform a retrospective, case-control study among military personnel estimating the vaccine efficacy of smallpox vaccine against mpox. From July 1 to Oct. 31, 2022, 1,014 military personnel presented with a clinical presentation concerning for mpox; 293 (29%) tested positive for orthopoxvirus. Of these, 121 (41%) were human immunodeficiency virus (HIV)-positive. Nineteen (10%) of those followed exclusively at the VA required hospitalization, and none died.
Looking at the larger cohort, 10 (3%) had received Dryvax and 20 (7%) had received ACAM2000 a median of 13 years earlier (interquartile range, 6 to 20 years). Individuals who had received either smallpox vaccine were significantly less likely to test positive for mpox. The estimated vaccine efficacy against mpox was 72% for Dryvax and 75% for ACAM2000. Data broken out by HIV infection was not provided.
These estimates of smallpox vaccine efficacy against mpox are similar to that reported for the Jynneos vaccine. In a review of three published clinical studies of Jynneos vaccine (by Stan Deresinski in Infectious Disease Alert, July 2023), vaccine efficacy against mpox ranged from 41% to 75% for a single dose and 66% to 89% for two doses. However, vaccine efficacy for a single dose of Jynneos vaccine in persons with HIV was as low as 36%. Thus, it appears that previous smallpox vaccination may be similarly effective against mpox as the current Jynneos vaccine.
Current guidelines for adults and adolescents with HIV continue to recommend two doses of Jynneos vaccine for individuals at risk who received smallpox vaccination more than 10 years earlier.1 While a booster dose is recommended at two years for those working with more virulent orthopoxviruses, as well as a booster dose at 10 years for those working with less virulent orthopoxviruses, there have not been recommendations yet for booster dosing of Jynneos in persons at risk.
REFERENCE
- ClinicalInfo.HIV.gov. Guidelines for the prevention and treatment of opportunistic infections in adults and adolescents with HIV. Sept. 27, 2023. https://clinicalinfo.hiv.gov/en/guidelines/hiv-clinical-guidelines-adult-and-adolescent-opportunistic-infections/immunizations
CLABSI Prevention
SOURCE: O’Grady NP. Prevention of central line-associated bloodstream infections. N Engl J Med 2023;389:1121-1131.
Prevention of central line-associated bloodstream infection (CLABSI) has become a major part of the hospital-acquired infection (HAI) reduction effort. CLABSIs result in significant increases in hospital stay, intensive care unit (ICU) days, mortality, and hospital cost. Efforts to reduce CLABSI seemed to have been paying off, at least until the COVID pandemic, when CLABSI rates substantially increased (along with other HAIs).
One issue in any assessment of CLABSI burden is the differentiation between National Healthcare Safety Network (NHSN)-defined CLABSI, and what we infectious disease physicians refer to as “real line infections,” or what has become known as catheter-related bloodstream infection (CRBSI). While CLABSI is defined as a bloodstream infection in a patient with a central venous line catheter for at least 48 hours, with no other source for the bacteremia or fungemia identified — in reality, formally reported CLABSI are wildly over-defined by this definition. It drives me crazy on Infection Prevention rounds when we end up with an NHSN-defined gram-negative CLABSI in a bowel-obstructed dying cancer patient that clearly is related to their underlying malignancy, simply because we have not attempted to culture something from the abdomen.
On the other hand, CRBSIs are a truer approximation of a real line infection and require clinical interpretation, e.g., a bloodstream infection with signs and symptoms of infection (not due to something else), leukocytosis, pain or erythema at the catheter site, a positive catheter tip culture, or possibly a differential quantitative blood culture result indicating the line was the source, and a response to therapy without necessarily removing the line or the indwelling port. The only problem is the interpretation of CRBSI requires expert assessment. When examining data related to central line infections, you need to know whether you are talking CLABSI or CRBSI.
While efforts to reduce CLABSIs primarily have been directed at ICU patients, the majority of CLABSIs now occur in non-ICU patients — and possibly outpatient parenteral antimicrobial therapy (OPAT) patients (although there is no systemic way to collect these data). Infections associated with lines are increased in cancer patients and those with neutropenia, patients receiving total parenteral nutrition, burn victims, patients with obesity (body mass index > 40), and prematurity in infants. In addition, the insertion site and technique, the number of lumens, the indications for use, the care of the catheter in hospital, and nursing ratios all have become a focus of CLABSI reduction interventions, as outlined later.
Proven strategies for CLABSI reduction include central line checklists, catheter-insertion kits, dedicated line teams, sterile barriers during insertion, and hand hygiene. Add to these the following interventions with varying levels of supportive data:
• Central line insertion site selection. The subclavian site of insertion has been demonstrated in the ICU setting to result in a reduction in CLABSI compared with femoral or internal jugular (but not compared with percutaneous catheters), but it is less clear whether the subclavian vein site is optimal in the non-ICU setting. Reduction in line infection must be balanced with the risk of pneumothorax and the patient circumstance.
• Alcoholic chlorhexidine (CHG) skin antiseptics at the time of catheter insertion. Multiple studies have shown a 27% overall reduction in CLABSI with CHG skin prep than with povidone iodine. Adequate dry times are important to the success of either product.
• CHG dressings. Dressings containing CHG (either gel-based or impregnated sponge dressings) covering the catheter exit site have been decidedly shown to reduce bloodstream infection and now are considered an “essential practice.” Dressings remain active for up to seven days, allowing for less frequent dressing changes. My only comment is the personal observation that these dressings do not always adhere well to the skin, especially in patients with heavy beards or with tracheal secretions and/or drooling.
• CHG bathing. Earlier randomized clinical trials demonstrated a likely benefit from daily CHG bathing in the ICU setting. However, some of these studies were confounded by the additional measure of mupirocin nasal decolonization for carriers of Staphylococcus aureus. The data are less clear in non-ICU patients. One study demonstrated a 60% benefit in CLABSI reduction in patients with hematologic malignancy with daily CHG bathing compared to standard of care. CHG bathing now is becoming de rigueur in the ICU setting and is being extended to long-term care.
• Antibiotic- and antiseptic-impregnated catheters. Most studies involving antibiotic- and antiseptic-impregnated catheters were conducted before CHG bathing became the standard of care. Thus, it is not clear whether all three interventions (CHG dressings, CHG daily bathing, and antiseptic-impregnated catheters) are required.
• Antiseptic-containing hubs and caps. Anyone who listened to Dr. Leonard Mermel, Professor of Medicine, Warren Alpert Medical School of Brown University, give his talk at IDWeek 2023 heard an impassioned argument for alcohol-containing needleless hubs in the reduction of CLABSIs. He argued that most CLABSIs do not occur as the result of skin contamination crawling along the exterior of the catheter, but as the result of environmental or skin contamination of the connectors. He argued that the 5-6 seconds for the hospital nurse to use an alcohol swab to disinfect a port is a time-limiting event and not sufficiently effective. In a recent meta-analysis involving 15 studies, the risk of bloodstream infection was significantly reduced by the use of an alcohol-containing end cap (port protector) compared with standard of care (391 events/273,993 lines vs. 620 events/284,912 lines; odds reduction, 0.65).1
An unresolved issue was whether mechanical disinfection of an alcohol-impregnated hub still was required. A recent study nicely answered this question — demonstrating the frequency of contamination of the hub with a five-second alcohol wipe as standard of care (58%) vs. the alcohol-containing hub alone (1.2%) vs. a mechanical alcohol wipe of an alcohol-containing hub (0.6%) (data not yet published). The conclusion was that “the use of an antiseptic-containing cap or hub precludes the need for additional disinfection.” This high-quality evidence should prompt a change from the current practice of manual disinfection of the hub in accessing a central line catheter to the use of port protectors.
• Data capture and CLABSI definition. Some argue that simpler definitions of CLABSI should be created to allow for computerized capture of data. I would argue the opposite. The determination of central line infection requires experienced interpretation of complex data and the consideration of patient circumstance, as well as the clinical response to specific types and duration of treatment — something the current NHSN definition does not take into account. Infection prevention teams already are trained to perform a similar function for surgical site infection reviews.
REFERENCE
- Gillis VELM, van Es MJ, Wouters Y, Wanten GJA. Antiseptic barrier caps to prevent central line-associated bloodstream infections: A systematic review and meta-analysis. Am J Infect Control 2023;51:827-835.
Smallpox Vaccination Effective Against Mpox; CLABSI Prevention
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