According to the Centers for Disease Control and Prevention (CDC) of the United States, 1282 cases of measles were confirmed across 31 states in 2019, with most cases found among unvaccinated individuals. This number represents a 341% increase from the previous year and also the greatest number of cases reported in the country since 1992, which highlights the importance of building a safe and strong immunologic response to prevent diseases that viruses like measles, mumps, and rubella (MMR) might cause.¹

A common clinical finding among patients with multiple myeloma (MM), a hematological malignancy resulting from the clonal expansion of plasma cells, is the suppression of immune function due to underlying disease and/or chemotherapy-based treatments. Standard of care for newly diagnosed MM consists of one or multiple lines of induction therapy combining steroids, proteasome inhibitors (PI), and immunomodulatory agents (IMiD), followed by an autologous stem cell transplant (ASCT) in all eligible candidates.² Furthermore, we are likely to add monoclonal antibodies that target CD38 as part of four drug regimens.

It is known that ASCT recipients experience a decline in antibody titers to vaccine-preventable illnesses post-transplant, particularly those who have previously received multiple lines of chemo-immunotherapy.³ Additionally, prior studies have demonstrated that MMR revaccination among these patients is necessary, effective, and safe after the procedure, even when followed by lenalidomide or bortezomib maintenance therapy.⁴ Current guidelines recommend revaccination with live attenuated vaccines such as MMR 2 years after ASCT.

A primary objective of this study is to evaluate whether the advent of novel therapeutics, which has greatly improved disease outcomes and duration of disease control, followed by ASCT would result in decreased humoral immunity against common childhood diseases. If so, earlier post-ASCT vaccination boost would likely be indicated. Furthermore, studying the effects of therapy plus ASCT on long-lasting immunity will be of relevance to understand the effects of ASCT on COVID-19 immunity.

We analyzed 110 patients diagnosed with MM (age range from 25 to 75 years old, median 60 years) that had been seen at Mayo Clinic Arizona (MCA). Of these, 60% were male (66) and 57.3% (63) were born before 1957 (Table S1), which makes them presumably immune against MMR due to natural infection. The vaccination status of the remaining patients was unknown. All patients had received one or multiple lines of therapy and subsequently underwent ASCT between 2014 and 2019. We selected one sample per individual within approximately 100 days after ASCT (median 92 days, range 24–255 days), from the MCA tissue bank and extracted 800 microliters (μL) of plasma that was used for serologic testing (after Institutional Review Board approval). In the relapsed patients who had received a second salvage transplantation (N = 14), the analysis was performed in the sample collected after the most recent ASCT.

The predominant MM subtype, found in 32 patients (29.1%), was IgG Kappa. The main chemotherapy regimens received immediately prior to ASCT were VRd (bortezomib + lenalidomide + dexamethasone) in 44 patients (40%), CyBorD (cyclophosphamide + bortezomib + dexamethasone) in 22 (20%) and KRd (carfilzomib + lenalidomide + dexamethasone) in 14 (12.7%). Additional induction therapies, including monoclonal antibodies such as daratumumab and isatuximab, were provided depending on risk stratification of the disease, stage, tolerance, toxicity, and other prognostic factors.

As a control, we utilized an assay from the clinical laboratory representing fully vaccinated health care workers (HCWs) ranged in age from 21 to 51 years old (median, 37 years), a population younger than our MM patients, with presumed immunity to MMR, and evaluated for presence of MMR IgG antibodies.⁵ The serum samples for subjects in the MM patient group and the HCW group were tested using the same laboratory, equipment, and method (see below). Additionally, pre-ASCT samples were available in 45 of the 110 MM patients (median number of days prior to ASCT of 130; range 7–1925) and the IgG antibody levels were compared with the post-ASCT samples.

We performed the IgG multiplex flow immunoassay (MFI) using the Bio-Rad MMRV (measles, mumps, rubella, and varicella zoster virus) on the Bio-Rad BioPlex 2200 system (Bio-Rad Laboratories, Hercules, CA). This assay is FDA approved and was used according to manufacturer instructions for the simultaneous detection of IgG antibodies to MMRV in plasma samples as described previously.⁶ Flow cytometry is used to determine whether IgG antibodies are present against each of the viral targets and a fluorescence ratio (FR) is established by dividing the sample relative fluorescence intensity (RFI) by the internal standard bead fluorescence signal. The FR is subsequently compared to the assay-specific calibration curve to establish an analyte-specific antibody index (AI). For measles and mumps, AI values of ≤ 0.8, 0.9–1.1, and ≥ 1.1 are interpreted as negative, equivocal, and positive for the presence of IgG-class antibodies to these viruses, respectively. The interpretive criteria for IgG-class antibodies to rubella are as follows: ≤ 0.7 AI, negative; 0.8–0.9 AI, equivocal; and ≥ 1.0 AI, positive.

Differences in the presence of IgG-class antibodies from pre-ASCT to post-ASCT where assessed via McNemar's chi-squared test. Differences in antibody presence among those born before 1957 versus those born in or after 1957 was assessed via Pearson's chi-squared test. p-values less than .05 were considered statically significant. All analyses were completed in R version 3.6.

Of 110 MM patients, 77 had positive measles titers after ASCT (Table 1). This represents 70% prevalence, versus 77.4% (154 out of 199) of the HCWs with a documented 2-dose measles vaccination history. With mumps, 49.1% (54/110) of the MM population showed positive IgG-class antibodies versus 84.8% (167/197) of the presumptively immune HCWs. Finally, 64.5% (71/110) of the MM cohort tested positive for IgG anti-rubella in comparison with 83.7% (175/209) of the HCWs who received at least one dose of rubella vaccine.

The comparison of the pre-ASCT samples versus post-ASCT in 45 MM patients showed mild variations in the overall number of individuals with positive IgG antibodies detected against any of the three viruses, despite the effects of induction therapy plus transplant (Table 1). There are very few discrepancies in equivocal results becoming negative after ASCT (one case in measles, three in mumps and one in rubella).

Finally, we found statistical significance (Pearson's chi-squared test) among the MM patients seropositive for anti-measles, post ASCT, based on their year of birth (Table S2). Of the 63 patients born before 1957 and presumably immune after natural exposure to the virus, 82.5% (52) showed positive IgG antibodies versus 53.2% (25 of 47) born in 1957 or after (p = .001). The same tendency is observed in mumps (p value not significant) and rubella (p = .01), with higher prevalence in those born before 1957 (55.6% and 76.2%, respectively) versus the rest (40.4% and 48.9%, respectively).

In conclusion, our findings show sustained immunity in most patients and no ubiquitous decrease in titers levels that could presumably be attributed to the immunosuppressive effect of novel MM treatments plus ASCT. Consequently, there is no strong evidence to contemplate earlier revaccination. Consideration to measure viral titers individually might be appropriate to better ascertain the need for repeating vaccination.

This study has some limitations. Initially, the assay is not calibrated to the World Health Organization standard to detect protective levels of immunity against measles and mumps, but rather whether any antibodies to these viruses are present. The anti-rubella IgG it is the only assay referenced against the true level of protective antibodies.

Second, as mentioned, we did not know, nor did we have access to documentation of the patients' vaccination status during their childhood. At the same time, we recognize that the incidence of measles, mumps, and rubella in a resource-rich nation such as the United States is exceedingly low, and that MM patients represent an even smaller fraction of those that may potentially be impacted by these illnesses. However, our study is important as it relates more to enduring immunity and supports persistence of immunity post-transplant.

Additional studies are needed to establish the level at which detected antibodies confer protective immunity for both measles and mumps viruses, and whether the statistical significance of birth year variances in IgG durability is further borne out. Furthermore, we found a remarkable variance in the seropositive percentages for anti-mumps and anti-rubella in MM patients after transplant versus the control population that might require further investigation.

At first glance, our results suggest a more durable immunity associated with infection, versus the resulting from immunization, an observation that will be of relevance as well for COVID-19 and other infections. While our cohort cannot test for SARS-CoV2 antibodies, based on our observations, it is likely that those who have been vaccinated or who have recovered from infection will remain protected if they undergo an ASCT.

根据美国疾病控制和预防中心 (CDC) 的数据，2019 年在 31 个州确诊了 1282 例麻疹病例，其中大多数病例是在未接种疫苗的人群中发现的。这一数字比上一年增加了 341%，也是该国自 1992 年以来报告的病例数最多的一次，这凸显了建立安全和强大的免疫反应以预防麻疹、腮腺炎和风疹等病毒疾病的重要性。 MMR）可能会导致。¹

多发性骨髓瘤 (MM) 是一种由浆细胞克隆扩增引起的血液系统恶性肿瘤，其常见的临床发现是由于潜在疾病和/或基于化疗的治疗导致免疫功能受到抑制。新诊断 MM 的护理标准包括一种或多种诱导疗法，结合类固醇、蛋白酶体抑制剂 (PI) 和免疫调节剂 (IMiD)，然后对所有符合条件的候选人进行自体干细胞移植 (ASCT)。²此外，我们可能会在四种药物方案中添加靶向 CD38 的单克隆抗体。

众所周知，ASCT 接受者在移植后对疫苗可预防疾病的抗体滴度下降，尤其是那些先前接受过多种化学免疫疗法的人。³此外，先前的研究表明，这些患者在手术后重新接种 MMR 是必要的、有效的和安全的，即使在随后进行来那度胺或硼替佐米维持治疗时也是如此。⁴目前的指南建议在 ASCT 后 2 年使用减毒活疫苗（如 MMR）再次接种。

本研究的一个主要目的是评估新疗法的出现是否会导致对常见儿童疾病的体液免疫降低，这种疗法极大地改善了疾病结果和疾病控制的持续时间，随后进行了 ASCT。如果是这样，可能会指示更早的 ASCT 后疫苗接种加强。此外，研究治疗加 ASCT 对持久免疫的影响将有助于了解 ASCT 对 COVID-19 免疫的影响。

我们分析了在亚利桑那州梅奥诊所 (MCA) 就诊的 110 名诊断为 MM（年龄范围为 25 至 75 岁，中位数为 60 岁）的患者。其中，60% 为男性（66 人），57.3%（63 人）出生于 1957 年之前（表 S1），这使得他们可能因自然感染而对 MMR 免疫。其余患者的疫苗接种情况未知。所有患者都接受了一种或多种治疗，随后在 2014 年至 2019 年期间接受了 ASCT。我们在 ASCT 后约 100 天内（中位 92 天，范围 24-255 天）从 MCA 组织库中为每个个体选择了一个样本并提取用于血清学检测的 800 微升 (μL) 血浆（在机构审查委员会批准后）。在接受第二次挽救性移植的复发患者中（N = 14），分析是在最近一次 ASCT 后收集的样本中进行的。

在 32 名患者 (29.1%) 中发现的主要 MM 亚型是 IgG Kappa。在 ASCT 前立即接受的主要化疗方案是 VRd（硼替佐米 + 来那度胺 + 地塞米松）44 例（40%），CyBorD（环磷酰胺 + 硼替佐米 + 地塞米松）22 例（20%）和 KRd（卡非佐米 + 来那度胺 + 地塞米松） 14 (12.7%)。根据疾病的风险分层、分期、耐受性、毒性和其他预后因素，提供了额外的诱导治疗，包括 daratumumab 和 isatuximab 等单克隆抗体。

作为对照，我们使用了来自临床实验室的检测，该检测代表年龄在 21 至 51 岁（中位数为 37 岁）之间完全接种疫苗的医护人员（HCW），该人群比我们的 MM 患者年轻，推测对 MMR 有免疫力，并评估 MMR IgG 抗体的存在。⁵ MM 患者组和 HCW 组受试者的血清样本使用相同的实验室、设备和方法进行检测（见下文）。此外，110 名 MM 患者中有 45 名获得了 ASCT 前样本（ASCT 前的中位天数为 130；范围 7-1925），并将 IgG 抗体水平与 ASCT 后样本进行了比较。

我们在 Bio-Rad BioPlex 2200 系统（Bio-Rad Laboratories，Hercules，CA）上使用 Bio-Rad MMRV（麻疹、腮腺炎、风疹和水痘带状疱疹病毒）进行了 IgG 多重流动免疫测定 (MFI)。该测定已获得 FDA 批准，并根据制造商说明用于同时检测血浆样品中 MMRV 的 IgG 抗体，如前所述。⁶流式细胞术用于确定是否存在针对每个病毒靶标的 IgG 抗体，并通过将样品相对荧光强度 (RFI) 除以内标珠荧光信号来建立荧光比 (FR)。随后将 FR 与测定特异性校准曲线进行比较，以建立分析物特异性抗体指数 (AI)。对于麻疹和腮腺炎，≤ 0.8、0.9–1.1 和 ≥ 1.1 的 AI 值分别被解释为存在针对这些病毒的 IgG 类抗体的阴性、模棱两可和阳性。风疹 IgG 类抗体的解释标准如下： ≤ 0.7 AI，阴性；0.8–0.9 AI，模棱两可；并且 ≥ 1.0 AI，阳性。

通过 McNemar 的卡方检验评估从 ASCT 前到 ASCT 后 IgG 类抗体存在的差异。通过 Pearson 的卡方检验评估 1957 年之前出生的人与 1957 年或之后出生的人之间抗体存在的差异。小于 0.05 的p值被认为具有静态显着性。所有分析均在 R 版本 3.6 中完成。

在 110 名 MM 患者中，77 名在 ASCT 后麻疹滴度呈阳性（表 1）。这代表 70% 的患病率，而有 2 剂麻疹疫苗接种史的 HCW 的患病率是 77.4%（199 名中的 154 名）。对于腮腺炎，49.1% (54/110) 的 MM 人群显示出阳性 IgG 类抗体，而推定免疫 HCW 的这一比例为 84.8% (167/197)。最后，MM 队列中有 64.5% (71/110) 的 IgG 抗风疹病毒检测呈阳性，而接受至少一剂风疹疫苗的医护人员中有 83.7% (175/209) 的比例为 83.7% (175/209)。

45 名 MM 患者的 ASCT 前样本与 ASCT 后样本的比较显示，尽管诱导治疗加移植有效果，但检测到针对三种病毒中任何一种的 IgG 抗体阳性的个体总数略有差异（表 1）。在 ASCT 后模棱两可的结果变为阴性的差异很少（麻疹病例 1 例，腮腺炎病例 3 例，风疹病例 1 例）。

最后，我们发现在 ASCT 后抗麻疹血清反应阳性的 MM 患者中，基于他们的出生年份具有统计学意义（Pearson 卡方检验）（表 S2）。在 1957 年之前出生且在自然接触病毒后可能免疫的 63 名患者中，82.5% (52) 显示出 IgG 抗体阳性，而 1957 年或之后出生的患者为 53.2% (47 人中的 25 人) ( p  = .001)。在流行性腮腺炎（ p值不显着）和风疹（p = .01）中观察到相同的趋势 ，1957 年之前出生的人（分别为 55.6% 和 76.2%）的患病率高于其他人（分别为 40.4% 和 48.9%） ）。

总之，我们的研究结果表明，大多数患者具有持续的免疫力，并且滴度水平没有普遍降低，这可能归因于新型 MM 治疗加 ASCT 的免疫抑制作用。因此，没有强有力的证据可以考虑提前重新接种疫苗。考虑单独测量病毒滴度可能适合更好地确定重复接种疫苗的需要。

这项研究有一些局限性。最初，该检测方法并未根据世界卫生组织标准进行校准，以检测针对麻疹和腮腺炎的免疫保护水平，而是根据是否存在针对这些病毒的抗体进行校准。抗风疹 IgG 它是唯一参考保护性抗体真实水平的检测方法。

其次，如前所述，我们不知道，也无法获得患者童年时期疫苗接种状况的文件。同时，我们认识到，在美国等资源丰富的国家，麻疹、腮腺炎和风疹的发病率极低，而 MM 患者在可能受这些疾病影响的患者中所占比例甚至更小。疾病。然而，我们的研究很重要，因为它更多地涉及持久免疫并支持移植后免疫的持久性。

需要进一步的研究来确定检测到的抗体对麻疹和腮腺炎病毒的保护性免疫水平，以及是否进一步证实出生年份差异对 IgG 持久性的统计意义。此外，我们发现移植后 MM 患者的抗腮腺炎和抗风疹血清阳性百分比与可能需要进一步调查的对照人群相比存在显着差异。

乍一看，我们的研究结果表明，与免疫接种产生的免疫力相比，与感染相关的免疫力更持久，这一观察结果也与 COVID-19 和其他感染相关。虽然我们的队列无法测试 SARS-CoV2 抗体，但根据我们的观察，那些已接种疫苗或从感染中恢复的人如果接受 ASCT，很可能仍将受到保护。