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Here is a summary of some of the key questions that have arisen for people with multiple sclerosis as countries roll out their COVID-19 vaccination programs.

Should I get vaccinated against COVID-19 if I have MS?

Yes. COVID-19 disease can have serious complications; the overall mortality rate is about 3-5% but can be much higher in at-risk groups. In addition, about 5% of adults people experience persistent problems (called ‘long COVID’), such as difficulty breathing, headache and fatigue (García-Abellán et al. medRxiv preprint, 8 March 2021). Children generally have less severe symptoms but appear to have a higher risk of persistent symptoms (Buonsenso et al. medRxiv preprint, 26 January 2021).

Who has a higher risk of severe COVID?

People with MS do not appear to have a higher risk of severe COVID. People who need to take extra precautions are older individuals (age 50 or older), people who are more disabled (i.e. requiring walking assistance), and people with MS and another medical condition, such as diabetes, lung diseases, kidney disease, and heart disease (Salter et al. ECTRIMS 2020; LB1242.). Obesity (a body-mass index [BMI] of 30 or more) appears to double the risk of developing severe COVID (Hussain and colleagues. Obes Res Clin Pract 2020;14: 295-300). (To calculate your BMI go to:

Will COVID vaccination worsen my MS?

This is unlikely. While the current assortment of COVID vaccines have not been specifically tested in people with MS, they do not contain live virus so they would not be expected to have an impact on the MS disease process and should not cause a relapse. That said, vaccines can cause mild-to-moderate symptoms, such as headache or fever, which may cause a short-term worsening of some MS symptoms. But these symptoms are not a relapse and should get better shortly. It may be helpful to take Tylenol to relieve the symptoms (

Are some vaccines more effective than others?

The Pfizer and Moderna vaccines (which use similar technology) appear to be the most effective; their efficacy in preventing COVID has been reported to be about 95% (Polack and colleagues. N Engl J Med 2020; epublished December 10, 2020). The efficacy of the AstraZeneca vaccine is about 62% (Health Canada, Feb. 26, 2021). The Johnson & Johnson vaccine (which uses technology that is similar to the AstraZeneca vaccine) defined “efficacy” as preventing a moderate/severe case of COVID (rather than getting COVID); its efficacy was 66%.

The Pfizer, Moderna and AstraZeneca vaccines require two doses; the J&J vaccine only needs one dose. It is important to note that the expected efficacy is based on the dosing that was done in clinical trials. The two Pfizer shots were given 21 days apart, the Modera vaccine 28 days apart, and the AstraZeneca vaccine at various times (4-12 weeks apart is recommended). As the vaccination roll-out proceeds, many governments have opted to delay the second dose so as to achieve partial vaccination of more people. There are no data on whether a delayed second dose will affect the efficacy of vaccination.

While you may prefer one vaccine over another, it is unlikely that governments, which are having problems with the rollout, will provide much choice – people have been told to take what is offered.

Once vaccinated, immunity takes a couple of weeks to develop so it is important to maintain the usual precautions – hand washing, physical distancing and wearing a mask – even after you have received your shots. This is especially so for at-risk individuals (see above).

What are variants?

Viruses can mutate every time they reproduce; as more people get infected, there is an increasing likelihood that mutations will emerge. So it is not surprising that variant strains have appeared during the global pandemic. Of the many mutations that can occur, there are two types that are of particular concern. The first type includes mutations that affect the outer spikes on the virus, which enable the virus to attach to cells in the body and infect them. Mutations that make this attachment more efficient mean that the virus is more transmissible. Secondly, vaccines target these spike proteins. If the spike structure is changed by a mutation, the immune system has a harder time detecting and killing the virus, meaning that vaccines become less effective. Thus far, countless COVID variants have emerged but three have attracted particular attention: the UK strain (called B.1.17), the South African strain (called B. and the Brazil strain (called P.1). All three have been detected in Canada and the U.S. All are more infectious than the original strains, so variants are likely to become the dominant strains later this year (just as its predecessor became dominant over the original Chinese strain). The UK strain appears to be more easily transmitted and is associated with more severe COVID (Galloway and colleagues. MMWR, 22 January 2021;70:95-99. Challen and colleagues. Br Med J 2021;372:n579). The South Africa strain is also more transmissible and may be able to evade detection by the immune system (Wibmer and colleagues. bioRxiv 427166 preprint, 19 January 2021). The concern with the Brazil variant is that it may be able to cause COVID in people who have already had it (or been vaccinated).

Is vaccination effective against variants?

Variants appear to reduce the effectiveness of COVID vaccines (which may explain why the AstraZeneca and J&J vaccines, which were tested in people from South Africa and Brazil, were less effective). However, vaccination will likely confer some protection – it may not stop COVID, but it may prevent severe COVID. We will know more once more variant cases are reported. However, the emergence of variants underscores the importance of getting both shots of vaccine – the booster shot will provide additional protection. The vaccine manufacturers are now talking about whether a third shot may help and are now retooling the current vaccines to make them more effective against variant strains. This may well be an ongoing process, much like how the flu shot is modified every year to target new strains of the influenza virus.

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