University of Auckland: If you’ve recently had Covid, look out for shingles

There is growing evidence, both anecdotal and now in several studies, that shingles seems to be occurring at a greater rate in people shortly after Covid-19 infection than might otherwise be expected.

A large recent study in the US looked at people who had not received Covid or shingles vaccines and found that people who had had Covid were 15 percent more likely to develop shingles than the people who hadn’t. People who had been hospitalised for Covid were 20 percent more likely to develop shingles than people who hadn’t been infected with the virus.

Why might this be? Shingles is very common. There are an estimated 20,000 cases each year in New Zealand – about 55 new cases a day, so we would expect some cases to occur following a Covid-19 infection simply by chance. But investigations do suggest this involves more than chance and that there is a causal connection between Covid and shingles.

Shingles, aka herpes zoster, is a disease characterised by a painful rash that anyone who has ever had chickenpox is at risk of getting at least once at some time in their life. A 45-year-old woman has a more than 30 percent chance of developing shingles in her remaining lifetime, and a man of the same age slightly less. After 50, the risk steadily increases. If you live long enough, you have a very good chance of experiencing this disease. Shingles can be severe and serious, and also hard to treat, particularly if not identified very early.

Shingles is caused by the reactivation of the varicella zoster virus that causes chickenpox. After recovery from the pox, the virus enters the nervous system and remains dormant, usually kept at bay very effectively by your immune system – your T-cells in particular.

As we age or get stressed the immunity can fail and the virus wakes up and travels along the nerves to the skin. A painful rash appears. Anti-viral medication can be very effective if initiated early.

But for some people shingles can cause debilitating pain and a condition called post-hepatic neuralgia (an intermittent or persistent pain in the areas of skin affected by shingles) that can last months to years.

Early symptoms of shingles can vary between people. They often include numbness, tingling, itching, and burning pain, on one part of the body, most often around the torso.

These and other symptoms such as tiredness and fever can appear before the rash. The pain can get worse as shingles develops and people describe it as sharp, stabbing, and intense. The area might be very sensitive to touch. Shingles can sometimes be fatal.

Why would Covid increase your risk of shingles?

There appears no body organ system that is not a target for the Covid-19 virus, including the immune system. One part of the immune system that can suffer the ravages of Covid is the very part is needed to keep the shingles virus quiet. It is possible this is what underlies the connection between Covid and shingles. Research is ongoing.

Fortunately, there are now two vaccines available in New Zealand – Zostavax and Shingrix. Zostavax is funded for people aged 65 (not 64 nor 66). Zostavax is basically a more potent version of the chickenpox vaccine and quite effective at preventing the most severe shingles.

Protection lasts a few years and just one dose is required. However, as Zostavax contains a live virus it is not suitable for people with some immunosuppressive conditions who may be more at risk of adverse reactions from live vaccines.

Shingrix is a non-live vaccine, available for purchase for people over 50, and it is also safe for people with immune-related conditions. It is about 90 percent protective against shingles including in very old people, and protection appears to be long lasting.

The downside is that it is expensive – you won’t get a lot of change out of $350 per dose. The Government announced last month that Shingrix will replace Zostavax as the funded vaccine for people aged 65 later this year. If you are outside the eligible age group, you will still need to pay.

Hopefully, this vaccine might be funded for more people soon, especially if we see more shingles cases.

There have been reports that people have developed shingles after receiving their Covid vaccine, and speculation that the vaccine caused shingles. I have looked at the current literature and while there are certainly case reports and scientific investigations into those reports, the general expert opinion at this stage is there is little evidence to support a greater risk of shingles if you are vaccinated or not.

Research on this topic is ongoing and there are several possible mechanisms proposed so we will watch this space. However, so far any significant causal relationship with the Covid vaccine and shingles is unconvincing. Given more severe Covid increases the risk of shingles, there is a far greater risk of triggering shingles from severe Covid than from Covid vaccination.

The key messages here are to remain vigilant for the early signs of shingles; if you are at high risk of Covid complications then ensure you are up to date with your Covid-19 vaccines to keep the risk of severe disease to a minimum; and consider getting vaccinated against shingles.

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