Science is not a religion and hence scientific advice, unlike beliefs, change as new evidence emerges. When the COVID-19 pandemic started we had to formulate advice on DMT use and their impact on SARS-CoV-2 infection and COVID-19 based on scientific principles and evidence of other viral infections. I created a table to summarise my opinions and as evidence has emerged I have updated the table accordingly. I have also added in new columns for example on advice about shielding/quarantine and on vaccine readiness. I have just updated the table for a sixth time changing the risk category of rituximab and other anti-CD20 therapies with a warning that it appears that this class of therapy increases your chance of getting COVID-19 and possibly severe COVID-19. This change is based on data from the Swedish MS registry and the survey below done in Iran. In short being on rituximab doubles your risk of getting COVID-19 and there is a suggestion that it increases your risk of getting severe COVID-19. At the moment there is not enough evidence to be firm about the latter or to comment on mortality risk.
How rituximab increases your chances of getting COVID-19 suggests it either (1) increases your exposure to the SARS-CoV-2 virus, which to me is not plausible unless it is due to increased exposure to the virus as a result of attending hospitals for infusions, or (2) it reduces your chances of having an asymptomatic infection. The latter seems most likely and is meanable to study.
It now seems that immune responses to other human coronaviruses, the ones that cause the common cold, may cross-react with SARS-CoV-2 and help keep the virus in check and explains why some people get asymptomatic or mild infections. So just maybe having had that common cold last winter or the year before has given you some built-in protection against getting COVID-19 and severe COVID-19. However, if you were B-cell depleted from being on an anti-CD20 when you had that common cold your immune system doesn’t make the necessary high-quality or high-affinity cross-reactive antibodies that you now need to protect yourself from getting symptomatic COVID-19 and potentially severe COVID-19. Please note this is a hypothesis, but it can be tested by studying people with MS and other condition on anti-CD20 therapies and screening them for antibodies against coronaviruses and comparing them to age-matched controls and patients on other DMTs. I am prepared to bet you the anti-CD20ers don’t have these cross-reactive antibodies or if they do they are at a lower level (titre) and are non-neutralizing.
Another possibility is that anti-SARS-CoV-2 antibody responses, in particular IgM antibodies, help clear the virus and aid in a more rapid recovery from COVID-19 and milder disease. Therefore, if your anti-SARS-CoV-2 antibody response is delayed or blunted by being on an anti-CD20 therapy this will increases your chances of getting more severe COVID-19. Whether this contributes to you being less likely to have asymptomatic SARS-CoV-2 infection is unknown, but again this can be studied in carefully designed studies.
Should this emerging data on rituximab change clinical practice? If you are already on an anti-CD20 therapy there is little you can do about your preexisting immunity to community-acquired coronaviruses; you either have immunity or you don’t. Similarly, you can’t simply revere the action of anti-CD20 therapies it takes months to years to reconstitute your peripheral B-cell pool. This is why I am now recommending that if you are on an anti-CD20 therapy you be extra-vigilant when it comes to trying to avoid being exposed to SARS-CoV-2 (social isolation, personal hygiene and avoiding high-risk environments). The good news is that the risk to individuals is low as a result of acquiring SARS-CoV-2 infection falls rapidly in most countries where anti-CD20 therapies are widely used to treat MS. I am still not recommending shielding because even though there is about a doubling of the risk of getting severe COVID-19 (hospitalization) the affected people with MS have been making a good recovery. The main determinants of death from COVID-19 in people with MS are older age, advanced disease and comorbidities and not the DMT they are on.
What about starting an anti-CD20 therapy? The decision to do this must be individualised and weighed against the risk of getting COVID-19. In countries where this risk is very low anti-CD20 therapies will be safe. The other issue that is emerging is vaccine readiness, i.e. having a peripheral immune system that is ready to respond to a SARS-CoV-2 vaccine if and when one emerges.
We know that people who are B-cell depleted, as a result of anti-CD20 therapies, make blunted vaccine responses. This is not surprising because anti-CD20 treated patients lack germinal centres in their lymph nodes and spleen. Germinal centres are the immunological equivalent of a university. It is in the germinal centres that T-cells help B-cell mature, class switch their antibodies, i.e. go from IgM to IgG for example, and to then undergo affinity maturation of the antibody genes to produce high-quality antibodies. Without germinal centres, your immune system can’t educate your B-cells to make high-quality antibodies and hence vaccine response will be poor. For people on anti-CD20 therapies, if they want to maximise your chances of responding to a vaccine you are going to have to pause your treatment to allow your immune systems to recover before receiving a coronavirus vaccine. When should you do this? I would not recommend this until a vaccine emerges; only cross bridges when they are built and if you need to cross them. There is still a relatively high chance that all of the 100+ SARS-CoV-2 vaccine candidates will fail; vaccine development for respiratory viruses is notoriously difficult.
At the moment the data we have from the Swedish registry and Iran is limited to rituximab but is likely to be relevant to ocrelizumab, ofatumumab and other anti-CD20 therapies. If you are conservative you may want to wait for the evidence base for these other anti-CD20 therapies to mature before incorporating the emerging evidence into your clinical decision-making. The good news is that there are several big data initiatives underway and we should report out within the next 1-2 months to confirm if this is a real signal, how robust the signal is and whether or not it applies to ocrelizumab and potentially other anti-CD20 therapies.
Does this have implications for other infectious diseases? I don’t know but I would not be surprised when we study the immune responses and outcomes to other viral infections, for example, seasonal influenza the same patterns may emerge. Now that we have set-up COVID-19 registries I would urge the MS community to keep them open so that we can study what happens with the next influenza epidemic that is only months away. The scary thought is what will happen if next season’s flu strain is a bad one? The impact of a more virulent flu strain on top of the tail of a SARS-CoV-2 pandemic is a scenario that makes me shudder. Do black swans ever emerge as twins?
Safavi et al B-cell depleting therapies may affect susceptibility to acute respiratory illness among patients with multiple sclerosis during the early COVID-19 epidemic in Iran. MSARDS Published:May 12, 2020.
Objective: To determine whether the course of COVID-19 is more severe in patients with MS and if MS disease-modifying treatments (DMTs) affect the risk of contracting the disease.
Methods: In a cross-sectional survey, data were collected by sending a questionnaire to 2000 patients with a demyelinating disease through an online portal system. Collected data included the current MS DMT and patient-reported disability level, history of recent sick contact, recent fever, respiratory symptoms, diagnosis with COVID-19, and the disposition after the diagnosis. We defined a COVID-19-suspect group as patients having fever and cough or fever and shortness of breath, or a presumptive diagnosis based on suggestive chest computed tomography. We calculated the proportion of COVID-19-suspect patients and compared their demographics, clinical characteristics, and DMT categories with the rest of survey-responders, using univariable and multivariable models.
Results: Out of 712 patients, 34 (4.8%) fulfilled our criteria for being in the COVID-19-suspect group. Only two patients required hospitalization. No patient required intensive care. In a multivariable model, disease duration (p-value=0.017), DMT category (p-value=0.030), and history of sick contact (p-values<0.001) were associated with the risk of being in the COVID-19-suspect group. Being on B-cell depleting antibodies (as compared to non-cell depleting, non-cell trafficking inhibitor DMTs) was associated with a 2.6-fold increase in the risk of being in the COVID-19-suspect group. (RR: 3.55, 95%CI: 1.45, 8.68, p-value=0.005).
Conclusions: The course of infection in patients with MS suspected of having COVID-19 was mild to moderate, and all patients had a full recovery. B-cell depleting antibodies may increase the susceptibility to contracting COVID-19.
Shen et al. Delayed Specific IgM Antibody Responses Observed Among COVID-19 Patients With Severe Progression. Emerg Microbes Infect. 2020 Dec;9(1):1096-1101.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly worldwide since it was confirmed as the causative agent of COVID-19. Molecular diagnosis of the disease is typically performed via nucleic acid-based detection of the virus from swabs, sputum or bronchoalveolar lavage fluid (BALF). However, the positive rate from the commonly used specimens (swabs or sputum) was less than 75%. Immunological assays for SARS-CoV-2 are needed to accurately diagnose COVID-19. Sera were collected from patients or healthy people in a local hospital in Xiangyang, Hubei Province, China. The SARS-CoV-2 specific IgM antibodies were then detected using a SARS-CoV-2 IgM colloidal gold immunochromatographic assay (GICA). Results were analysed in combination with sera collection date and clinical information. The GICA was found to be positive with the detected 82.2% (37/45) of RT-qPCR confirmed COVID-19 cases, as well as 32.0% (8/25) of clinically confirmed, RT-qPCR negative patients (4-14 days after symptom onset). Investigation of IgM-negative, RT-qPCR-positive COVID-19 patients showed that half of them developed severe disease. The GICA was found to be a useful test to complement existing PCR-based assays for confirmation of COVID-19, and a delayed specific IgM antibody response was observed among COVID-19 patients with severe progression.
The following slides show some of the data I refer to above:
If you want to watch the iWiMS Webinar it is on YouTube; the relevant section starts at about 21 minutes.