Eutectic mixture of local anesthetics and amethocaine as topical anesthetics in pediatrics: a meta-analysis.

BACKGROUND: Pediatric patients often receive topical anesthesia before skin procedures in the Emergency Department, with EMLA cream and amethocaine gel being common choices. The most effective option remains a subject of debate. OBJECTIVE: Our goal was to compare EMLA cream with amethocaine gel in pediatric patients undergoing topical anesthesia, focusing on outcomes: first-attempt cannulation success, child-reported visual analogue scale (VAS) score, parent-reported VAS score, observed pain score, child-reported absence of pain, and child-reported acceptable anesthesia. METHODS: A database search for studies comparing EMLA cream and amethocaine gel in pediatric topical anesthesia was conducted. Two reviewers extracted and cross-verified data, with a third ensuring accuracy. Using R software, a pairwise meta-analysis was performed via the Mantel-Haenszel method. Outcomes were pooled as risk ratios or standard mean differences with 95% confidence intervals using the random-effects model. RESULTS: Amethocaine gel surpasses EMLA cream in child-reported pain absence and first cannulation success. No significant differences were found in child-reported acceptable anesthesia or observed pain scores. Similarly, child- and parent-reported VAS scores showed no variations between EMLA and amethocaine. CONCLUSION: This analysis favors amethocaine gel for pediatric topical anesthesia. Further large randomized trials comparing EMLA cream and amethocaine gel in pediatric patients are warranted. IMPACT: Procedural pain is a major concern for pediatric patients, their families, and physicians. Topical anesthesia is routinely given prior to children undergoing skin-related procedures in the Emergency Department. In pediatric patients, topical anesthetics such as eutectic mixture of local anesthetics cream and amethocaine gel have proved to be pioneering in pain reduction, but the most effective method is often disputed. Presently, this is the most comprehensive pooled analysis of trials comparing EMLA cream and amethocaine gel in pediatric patients undergoing topical anesthesia. Amethocaine performed better with regards to child-reported absence of pain and first attempt cannulation success.

Unicompartmental knee arthroplasty revised to total knee arthroplasty versus primary total knee arthroplasty: A meta-analysis of matched studies.

BACKGROUND: Unicompartmental knee arthroplasty (UKA) offers a less invasive alternative to total knee arthroplasty (TKA), but is accompanied by a high revision risk. The aim of our study was to perform a meta-analysis comparing outcomes of UKA revised to TKA versus primary TKA, to assess if UKA is an effective treatment option, despite its potential need for revision. METHODS: Studies comparing matched cohorts of patients with UKA revised to TKA versus primary TKA were identified via the PubMed, Ovid EMBASE, and Scopus databases. The following outcome measures were compared between treatment modalities: postoperative reoperation or revision, total complications, range of motion, patient-reported outcome measures, and length of stay. RESULTS: Ten studies were included with 1,070 patients: 410 UKA to TKA and 660 primary TKA. At an average follow-up of 5.6 years in the UKA to TKA cohort and 5.7 years in the primary TKA cohort, there were no significant difference in risk of revision (p = 0.81), total complications (p = 0.54), range of motion (p = 0.09), or length of stay (p = 0.31). Both objective and functional Knee Society Score were significantly higher in patients with primary TKA (p < 0.01). However, there was no difference in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) or pain scores (p = 0.13 and p = 0.21, respectively). CONCLUSION: UKA revised to TKA produced comparable clinical and patient-reported outcomes to a primary TKA. UKA may be an effective treatment option in unicompartmental arthritis that would allow for improved functionality and satisfaction without the concern of outcomes deteriorating in patients where a revision becomes necessary.

Preexisting anticoagulation is an independent predictor of mortality in geriatric trauma patients - a retrospective cohort study.

Introduction: Preexisting anticoagulation is common among geriatric trauma patients. Geriatric trauma patients have a higher risk of mortality compared to younger patients. We sought to evaluate the association of preexisting anticoagulation with mortality in a group of geriatric trauma patients. Methods: A retrospective review of geriatric trauma patients was conducted for those admitted to a Level 1 trauma center from January 2018 to December 2020. Vital signs, demographics, injury characteristics, laboratory data, and mortality were all collected. Multivariable logistic regression analysis was performed for the association of preexisting anticoagulation and a primary endpoint of all-cause mortality. These groups were controlled for preexisting comorbidities, injury severity scores, and systolic blood pressure in the emergency department. Results: Four thousand four hundred thirty-two geriatric patients were admitted during the study period. This cohort was made up of 36.9% men and 63.1% women. Three thousand eight hundred fifty-nine (87.2%) were white; the average age was 81±8.5 years, and the median injury severity score (ISS) was 5. The mean systolic blood pressure was 150±32 mmHg, mean heart rate was 81±16 bpm, mean lactate was 2.3±1.3, mean hematocrit was 37.3±8.8, and mean international normalized ratio (INR) was 1.7±10.3. One thousand five hundred ninety-two (35.9%) patients were on anticoagulation (AC) upon presentation. One hundred and sixty-five (3.7%) mortalities were recorded. Multivariable logistic regression analysis results show that preexisting anticoagulation [ odds ratio (OR) 1.92, 95% CI 1.36-2.72] was independently predictive of death. The analysis was adjusted for systolic BP in the emergency department less than90 mmHg (OR 5.55, 95% CI 2.83-10.9), having more than 1 comorbidity (OR 2.30, 95% CI 1.57-3.38) and ISS (OR 1.13, 95% CI 1.10-1.15). Conclusion: Our study indicates that preexisting anticoagulation is associated with mortality among geriatric trauma patients.

Ross procedure versus pulmonary homograft versus mechanical valve versus bioprosthetic valve versus Ozaki procedure for surgical aortic valve replacement: a frequentist network meta-analysis.

BACKGROUND: There has been a resurgence in interest regarding the Ross procedure due to recent publications detailing positive long-term outcomes. Conversely, surgical aortic valve replacement (SAVR) with a pulmonary homograft (PH), mechanical (MV), bioprosthetic (BV), or the Ozaki procedure each has its own technical advantages and disadvantages. Therefore, we performed a network meta-analysis (NMA) comparing other alternatives to Ross procedure. METHODS: Medical databases were comprehensively searched for studies comparing the Ross procedure with AVR using a PH, MV, BV, or the Ozaki procedure. Outcomes were pooled as risk ratios (RR) with their 95% confidence intervals (95% CI). RESULTS: A total of 7816 patients were pooled for our NMA from 24 studies. Compared to Ross procedure, both BV and MV were associated with significantly higher rates of 30-day mortality of RR (2.37, 95% CI 1.20-4.67) and (1.88 95% CI 1.04-3.40), respectively, with no significant difference regarding PH or Ozaki. However, only MV was associated with a higher risk of 30-day stroke (RR 8.42, 95% CI 1.57-45.23) with no significant difference in the other alternatives, as well as 30-day MI which showed no significant differences between any of the aortic conduits compared to the Ross procedure. Regarding 30-day major bleeding, MV was associated with a higher when compared to the Ross procedure RR (4.58, 95% CI 1.94-10.85), PH was associated with a lower risk of major bleeding with RR (0.35, 95% CI 0.17-0.71), and BV showed no significant difference. With a mean follow-up duration of 8.5 years compared to the Ross procedure, BV, PH, and MV were associated with a higher risk of long-term mortality with RR (1.89, 95% CI 1.38-2.58), (1.38, 95% CI 1.0-1.87), and (1.94, 95% CI 1.52-2.47), respectively, with the Ozaki procedure showed no significant difference. Regarding long-term stroke-with a mean of 6.3-year follow-up duration-there were no significant differences between any of the aortic conduits compared to the Ross procedure. Nevertheless, long-term need for reintervention-with a mean follow-up duration of 17.5 years-was significant of higher risk with both BV and PH with RR (3.28, 95% CI 1.21-8.84) and (2.42, 95% CI 1.05-5.58), respectively, compared to Ross procedure with MV and Ozaki having no significant difference. CONCLUSIONS: The Ross procedure is a viable treatment option for patients undergoing SAVR, showing promising outcomes at short- and long-term follow-ups.

Opioid-free anesthesia versus opioid-based anesthesia in patients undergoing cardiovascular and thoracic surgery: a meta-analysis and systematic review.

BACKGROUND: Despite their extensive clinical use, opioids are characterized by several side effects. These complications, coupled with the ongoing opioid epidemic, have favored the rise of opioid-free-anesthesia (OFA). Herein, we perform the first pairwise meta-analysis of clinical outcomes for OFA vs opioid-based anesthesia (OBA) in patients undergoing cardiovascular and thoracic surgery. METHODS: We comprehensively searched medical databases to identify studies comparing OFA and OBA in patients undergoing cardiovascular or thoracic surgery. Pairwise meta-analysis was performed using the Mantel-Haenszel method. Outcomes were pooled as risk ratios (RR) or standard mean differences (SMD) and their 95% confidence intervals (95% CI). RESULTS: Our pooled analysis included 919 patients (8 studies), of whom 488 underwent surgery with OBA and 431 with OFA. Among cardiovascular surgery patients, compared to OBA, OFA was associated with significantly reduced post-operative nausea and vomiting (RR, 0.57; P = .042), inotrope need (RR .84, P = .045), and non-invasive ventilation (RR, .54; P = .028). However, no differences were observed for 24hr pain score (SMD, -.35; P = .510) or 48hr morphine equivalent consumption (SMD, -1.09; P = .139). Among thoracic surgery patients, there was no difference between OFA and OBA for any of the explored outcomes, including post-operative nausea and vomiting (RR, 0.41; P = .025). CONCLUSION: Through the first pooled analysis of OBA vs OFA in a cardiothoracic-exclusive cohort, we found no significant difference in any of the pooled outcomes for thoracic surgery patients. Although limited to 2 cardiovascular surgery studies, OFA was associated with significantly reduced postoperative nausea and vomiting, inotrope need, and non-invasive ventilation in these patients. With growing use of OFA in invasive operations, further studies are needed to assess their efficacy and safety in cardiothoracic patients.

General Anesthesia Versus Local Anesthesia in Patients Undergoing Transcatheter Aortic Valve Replacement: An Updated Meta-Analysis and Systematic Review.

OBJECTIVES: For patients with aortic stenosis, transcatheter aortic valve replacement (TAVR) offers a less invasive treatment modality than conventional surgical valve replacement. Although the surgery is performed traditionally under general anesthesia (GA), recent studies have described success with TAVR using local anesthesia (LA) and/or conscious sedation. The study authors performed a pairwise meta-analysis to compare the clinical outcomes of TAVR based on operative anesthesia management. DESIGN: A random effects pairwise meta-analysis via the Mantel-Haenszel method. SETTING: Not applicable, as this is a meta-analysis. PARTICIPANTS: No individual patient data were used. INTERVENTIONS: Not applicable, as this is a meta-analysis. MEASUREMENTS AND MAIN RESULTS: The authors comprehensively searched the PubMed, Embase, and Cochrane databases to identify studies comparing TAVR performed using LA or GA. Outcomes were pooled as risk ratios (RR) or standard mean differences (SMD) and their 95% CIs. The authors' pooled analysis included 14,388 patients from 40 studies (7,754 LA; 6,634 GA). Compared to GA TAVR, LA TAVR was associated with significantly lower rates of 30-day mortality (RR 0.69; p < 0.01) and stroke (RR 0.78; p = 0.02). Additionally, LA TAVR patients had lower rates of 30-day major and/or life-threatening bleeding (RR 0.64; p = 0.01), 30-day major vascular complications (RR 0.76; p = 0.02), and long-term mortality (RR 0.75; p = 0.009). No significant difference was seen between the 2 groups for a 30-day paravalvular leak (RR 0.88, p = 0.12). CONCLUSIONS: Transcatheter aortic valve replacement performed using LA is associated with lower rates of adverse clinical outcomes, including 30-day mortality and stroke. No difference was seen between the 2 groups for a 30-day paravalvular leak. These results support the use of minimally invasive forms of TAVR without GA.

Coronary Revascularization in Patients With Diabetes: A Meta-Analysis of Randomized Controlled Trials and Propensity-Matched Studies.

OBJECTIVE: Patients with diabetes have poorer outcomes with coronary artery disease (CAD) and pose a unique clinical population for revascularization. We performed a pairwise meta-analysis of randomized trials (RCTs) and propensity-matched observational studies (PMS) to compare the clinical outcomes of coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI) in patients with diabetes. METHODS: A comprehensive literature search was performed to identify RCT and PMS studies comparing CABG with PCI in patients with diabetes with concurrent CAD. Studies were pooled using the random-effects model to perform a pairwise meta-analysis. Primary outcomes included long-term all-cause mortality, cardiac mortality, myocardial infarction (MI), major adverse cardiac and cerebrovascular events (MACCE), and repeat revascularization. Meta-regression was used to explore the effects of baseline risk factors on primary outcomes with moderate to high heterogeneity. RESULTS: A total of 18 RCTs and 9 PMS with 28,846 patients were included. PCI was associated with increased long-term all-cause mortality (risk ratio [RR] = 1.34, P < 0.001), cardiac mortality (RR = 1.52, P < 0.001), MI (RR = 1.51, P = 0.009), MACCE (RR = 1.65, P < 0.001), and repeat revascularization (RR = 2.48, P < 0.001) compared with CABG. There was no difference in long-term stroke between the 2 groups (RR = 0.95, P = 0.82). At meta-regression, a greater proportion of female patients in studies was associated with a decreased protective benefit for CABG for long-term all-cause mortality but an increased protective benefit for long-term MI and repeat revascularization. CONCLUSIONS: Revascularization of patients with diabetes using CABG is associated with significantly reduced long-term mortality, MI, MACCE, and repeat revascularizations. Future studies exploring the influence of gender on revascularization outcomes are necessary to elucidate the ideal treatment modality in patients with diabetes.

Decellularized versus cryopreserved pulmonary allografts for right ventricular outflow tract reconstruction during the Ross procedure: a meta-analysis of short- and long-term outcomes.

BACKGROUND: The ideal conduit for repair of the right ventricular outflow tract (RVOT) during the Ross procedure remains unclear and has yet to be fully elucidated. We perform a pairwise meta-analysis to compare the short-term and long-term outcomes of decellularized versus cryopreserved pulmonary allografts for RVOT reconstruction during the Ross procedure. MAIN BODY: After a comprehensive literature search, studies comparing decellularized and cryopreserved allografts for patients undergoing RVOT reconstruction during the Ross procedure were pooled to perform a pairwise meta-analysis using the random-effects model. Primary outcomes were early mortality and follow-up allograft dysfunction. Secondary outcomes were reintervention rates and follow-up endocarditis. A total of 4 studies including 1687 patients undergoing RVOT reconstruction during the Ross procedure were included. A total of 812 patients received a decellularized pulmonary allograft, while 875 received a cryopreserved pulmonary allograft. Compared to cryopreserved allografts, the decellularized group showed similar rates of early mortality (odds ratio, 0.55, 95% confidence interval, 0.21-1.41, P = 0.22). At a mean follow-up period of 5.89 years, no significant difference was observed between the two groups for follow-up allograft dysfunction (hazard ratio, 0.65, 95% confidence interval, 0.20-2.14, P = 0.48). Similarly, no difference was seen in reintervention rates (hazard ratio, 0.54, 95% confidence interval, 0.09-3.12, P = 0.49) nor endocarditis (hazard ratio, 0.30, 95% confidence interval, 0.07-1.35, P = 0.12) at a mean follow-up of 4.85 and 5.75 years, respectively. CONCLUSIONS: Decellularized and cryopreserved pulmonary allografts are associated with similar postoperative outcomes for RVOT reconstruction during the Ross procedure. Larger propensity-matched and randomized control trials are necessary to elucidate the efficacy of decellularized allografts compared to cryopreserved allografts in the setting of the Ross.

Polyionic vaccine adjuvants: another look at aluminum salts and polyelectrolytes.

Adjuvants improve the adaptive immune response to a vaccine antigen by modulating innate immunity or facilitating transport and presentation. The selection of an appropriate adjuvant has become vital as new vaccines trend toward narrower composition, expanded application, and improved safety. Functionally, adjuvants act directly or indirectly on antigen presenting cells (APCs) including dendritic cells (DCs) and are perceived as having molecular patterns associated either with pathogen invasion or endogenous cell damage (known as pathogen associated molecular patterns [PAMPs] and damage associated molecular patterns [DAMPs]), thereby initiating sensing and response pathways. PAMP-type adjuvants are ligands for toll-like receptors (TLRs) and can directly affect DCs to alter the strength, potency, speed, duration, bias, breadth, and scope of adaptive immunity. DAMP-type adjuvants signal via proinflammatory pathways and promote immune cell infiltration, antigen presentation, and effector cell maturation. This class of adjuvants includes mineral salts, oil emulsions, nanoparticles, and polyelectrolytes and comprises colloids and molecular assemblies exhibiting complex, heterogeneous structures. Today innovation in adjuvant technology is driven by rapidly expanding knowledge in immunology, cross-fertilization from other areas including systems biology and materials sciences, and regulatory requirements for quality, safety, efficacy and understanding as part of the vaccine product. Standardizations will aid efforts to better define and compare the structure, function and safety of adjuvants. This article briefly surveys the genesis of adjuvant technology and then re-examines polyionic macromolecules and polyelectrolyte materials, adjuvants currently not known to employ TLR. Specific updates are provided for aluminum-based formulations and polyelectrolytes as examples of improvements to the oldest and emerging classes of vaccine adjuvants in use.

Increasing the potency of an alhydrogel-formulated anthrax vaccine by minimizing antigen-adjuvant interactions.

Aluminum salts are the most widely used vaccine adjuvants, and phosphate is known to modulate antigen-adjuvant interactions. Here we report an unexpected role for phosphate buffer in an anthrax vaccine (SparVax) containing recombinant protective antigen (rPA) and aluminum oxyhydroxide (AlOH) adjuvant (Alhydrogel). Phosphate ions bind to AlOH to produce an aluminum phosphate surface with a reduced rPA adsorption coefficient and binding capacity. However, these effects continued to increase as the free phosphate concentration increased, and the binding of rPA changed from endothermic to exothermic. Crucially, phosphate restored the thermostability of bound rPA so that it resembled the soluble form, even though it remained tightly bound to the surface. Batches of vaccine with either 0.25 mM (subsaturated) or 4 mM (saturated) phosphate were tested in a disease model at batch release, which showed that the latter was significantly more potent. Both formulations retained their potency for 3 years. The strongest aluminum adjuvant effects are thus likely to be via weakly attached or easily released native-state antigen proteins.

Recombinant protective antigen anthrax vaccine improves survival when administered as a postexposure prophylaxis countermeasure with antibiotic in the New Zealand white rabbit model of inhalation anthrax.

Inhalation anthrax is a potentially lethal form of disease resulting from exposure to aerosolized Bacillus anthracis spores. Over the last decade, incidents spanning from the deliberate mailing of B. anthracis spores to incidental exposures in users of illegal drugs have highlighted the importance of developing new medical countermeasures to protect people who have been exposed to "anthrax spores" and are at risk of developing disease. The New Zealand White rabbit (NZWR) is a well-characterized model that has a pathogenesis and clinical presentation similar to those seen in humans. This article reports how the NZWR model was adapted to evaluate postexposure prophylaxis using a recombinant protective antigen (rPA) vaccine in combination with an oral antibiotic, levofloxacin. NZWRs were exposed to multiples of the 50% lethal dose (LD(50)) of B. anthracis spores and then vaccinated immediately (day 0) and again on day 7 postexposure. Levofloxacin was administered daily beginning at 6 to 12 h postexposure for 7 treatments. Rabbits were evaluated for clinical signs of disease, fever, bacteremia, immune response, and survival. A robust immune response (IgG anti-rPA and toxin-neutralizing antibodies) was observed in all vaccinated groups on days 10 to 12. Levofloxacin plus either 30 or 100 µg rPA vaccine resulted in a 100% survival rate (18 of 18 per group), and a vaccine dose as low as 10 µg rPA resulted in an 89% survival rate (16 of 18) when used in combination with levofloxacin. In NZWRs that received antibiotic alone, the survival rate was 56% (10 of 18). There was no adverse effect on the development of a specific IgG response to rPA in unchallenged NZWRs that received the combination treatment of vaccine plus antibiotic. This study demonstrated that an accelerated two-dose regimen of rPA vaccine coadministered on days 0 and 7 with 7 days of levofloxacin therapy results in a significantly greater survival rate than with antibiotic treatment alone. Combination of vaccine administration and antibiotic treatment may be an effective strategy for treating a population exposed to aerosolized B. anthracis spores.

Epitope specificities of the group Y and W-135 polysaccharides of Neisseria meningitidis.

Previous studies have identified the length dependency of several polysaccharide (PS) protective epitopes. We have investigated whether meningococcal polysaccharides Y and W-135 possess such epitopes. Oligosaccharides (OSs) consisting of one or more disaccharide repeating units (RU) were derived from the capsular PSs of group Y and W-135 meningococci (GYMP and GWMP, respectively) by mild acid hydrolysis. The relative affinities of anticapsular antibodies binding to derivative OSs of different chain lengths were measured in inhibition enzyme-linked immunosorbent assays. As OS size increased from two to three RU, there was a notable increase in binding inhibition of rabbit anti-group Y antiserum. This pattern of antibody binding inhibition was also observed for rabbit antiserum to group W-135, though the inhibition increase was much more pronounced. In the cases of both OS species, the concentration of inhibiting antigen required to achieve 50% inhibition of rabbit immunoglobulin binding increased progressively as the inhibiting disaccharide chain length increased from 1 RU through greater than 50 RU. These data suggest that antibodies directed against both of these meningococcal PSs recognize conformational epitopes only fully expressed in higher-molecular-weight forms of these antigens.

Protective meningococcal capsular polysaccharide epitopes and the role of O acetylation.

Previous studies with group C meningococcal polysaccharide-tetanus toxoid (GCMP-TT) conjugates had suggested that the GCMP O-acetyl group masked the protective epitope for group C meningococci through steric hindrance or altered conformations. For this report, we confirmed this phenomenon and performed comparative studies with group Y meningococcal polysaccharide (GYMP)-TT to determine whether it might extend to other serogroups. The de-O-acetylated (dOA) polysaccharides (PSs) resulted in higher serum bactericidal activities (SBA) towards the O-acetylated (OA) meningococcal strains from the respective serogroups. High-resolution H-nuclear magnetic resonance spectroscopy at 500 MHz and competitive inhibition serum bactericidal assays were used to characterize the nature of the protective epitope. In head-to-head comparisons with OA PSs as SBA inhibitors, the dOA PSs provided 10 to 1,000 times better inhibition for GCMP in human and mouse antisera and 6 to 13 times better inhibition for GYMP in mouse antisera, using OA strains in all assays. In addition, the SBA for OA strains was highly correlated with dOA PS-specific immunoglobulin G (r=0.72 to 0.98) for both GCMP and GYMP. The results suggest that there may be a generalized role for the O-acetyl group to provide an epitope of misdirected immunogenicity for meningococcal PS capsules, enabling escape from immune surveillance. In addition to greater chemical consistency, the dOA forms of GCMP and GYMP conjugate vaccines endow greater immunologic competence to the PSs, rendering them capable of eliciting higher levels of functional antibodies toward the protective epitopes.

Specificity of the immune response to a modified group B meningococcal polysaccharide conjugate vaccine.

Antibodies to a modified group B meningococcal polysaccharide vaccine were examined for antigenic and functional specificities. Bactericidal determinants were investigated by using immunoaffinity columns and competitive inhibition of bactericidal activity in an in vitro killing assay. We conclude that nearly all of the vaccine-induced bactericidal activity is specific for the native polysaccharide.

Group B streptococcal type II and III conjugate vaccines: physicochemical properties that influence immunogenicity.

Recent efforts toward developing vaccines against group B streptococci (GBS) have focused on increasing the immunogenicity of GBS polysaccharides by conjugation to carrier proteins. However, partial depolymerization of GBS polysaccharides for the production of vaccines is a difficult task because of their acid-labile, antigenically critical sialic acids. Here we report a method for the partial depolymerization of type II and III polysaccharides by mild deaminative cleavage to antigenic fragments with reducing-terminal 2,5-anhydro-d-mannose residues. Through the free aldehydes of their newly formed end groups, the fragments were conjugated to tetanus toxoid by reductive amination. The resulting conjugates stimulated the production in animals of high-titer type II- and III-specific antibodies which induced opsonophagocytic killing of type II and III strains of group B streptococci. For the type II conjugates, immunogenicity increased as oligosaccharide size decreased, whereas for type III conjugates, the size of the oligosaccharides did not significantly influence immunogenicity. When oligosaccharides of defined size were conjugated through sialic acid residues, the resulting cross-linkages were shown to affect immunogenicity. When oligosaccharides were conjugated through terminal aldehyde groups generated by deamination, modification of the exocyclic chain of sialic acid did not influence immunogenicity.