Rare but serious blood clots that have been connected the AstraZeneca COVID-19 vaccine have many people — especially those who have already had one dose of the vaccine — searching for information. Here are answers to some important questions.

If I had a first dose of the AstraZeneca COVID-19 vaccine, if I have concerns about safety ?

As long as there’s a risk, you must remain aware and informed. A risk of very serious harm, including death, does exist, though it is extremely modest : about one in 55,000 for the first dose.

We now have a much better comprehension of how to diagnose and treat clotting due to COVID-19 vaccines, called vaccine-induced thrombotic thrombocytopenia, or VITT (also sometimes called vaccine-induced prothrombotic immune thrombocytopenia, or VIPIT) as it does occur. Death rates among individuals who experience VITT have been estimated at 20 to 50 percent , but might be advancing as knowledge increases. The Public Health Agency of Canada monitors all adverse events after COVID-19 vaccination.

It’s important that everyone who has had the AstraZeneca vaccine knows that it was the right thing to do. It’s an excellent and effective vaccine, and being vaccinated is a significant act to protect not just yourself, but your community by slowing and eventually stopping the pandemic.

Should I get a second dose of AstraZeneca? If so, when?

Getting the next dose of any two-step vaccine is quite important. This ’s what cements the memory of the immune reaction. We know from clinical trials that the first dose does not prevent all infections. It prevents death from infection. The second dose boosts the immune reaction to almost entirely protect you from getting any infection. That second dose also greatly reduces your ability to carry or spread the virus in any respect.

In terms of timing, evidence is still emerging, but the best advice regarding AstraZeneca is that a 12 to 20-week gap between first and second doses is perfect, much as it is with most vaccines.

Are the risks different for another dose?

The risk of a blood clot following a second dose is roughly one in 600,000, which is one-tenth the risk of clotting after an initial dose. In the event you were comfortable getting the initial dose, you should feel great about going ahead and continuing to help the community to bring the pandemic closer to its end. Additionally, knowing the symptoms associated with the vaccine-related clots allows for timely recognition and immediate therapy.

How serious a health hazard are blood clots that can follow a vaccine?

In those very rare cases where blood clots follow vaccination, they can be very serious and can be deadly. The good thing is that knowledge is progressing quickly, especially concerning diagnosing and treating these clots when they do occur.

Earlier in the vaccine rollout, the chance of death in the rare cases of clotting was 60 to 80%. Today, it’s 20%.

At the beginning of the rollout, patients had no method of knowing what a vaccine-related clot was or what to look for. That might have been a key element in the higher death rate. Now that this problem is known and the indicators can be identified, the risk of death is a lot lower. As we’ve progressed in understanding how this issue presents itself, people are being diagnosed and treated much earlier and more effectively.

Is it safe to get a different vaccine for my next dose?

Canada’s National Advisory Committee on Immunization urges that for another dose, you should stay with a vaccine made with the same technology “platform” as the first. If you first got AstraZeneca, which is a sort of viral vector vaccine, it’s recommended that you get it again. If it’s unavailable, Johnson and Johnson are just another viral vector vaccine.

If you had a vaccine based on an mRNA technology platform — Pfizer or Moderna — you can have either one of these two for your next dose. More data is emerging and mixing and matching platforms could ultimately be shown to be safe and effective, but for now, the recommendation is to remain with the same technology.

Are there any symptoms individuals should be watching for that may indicate a blood clot?

The symptoms of VITT are well recorded and include the following, which occur four or more days after vaccination:

  • Intense and persistent headaches.
  • Intense and persistent blurry eyesight.
  • Leg swelling.
  • Difficulty breathing.
  • Abdominal pain.
  • Bruising beyond the vaccination site.

It’s important to seek prompt medical care in these circumstances. It is also important to remember the minor fever, headache, fatigue and pain at the site of the vaccination are common with all vaccines in the first one or two days and aren’t causes for concern.

Who’s at risk from clotting associated with the AstraZeneca vaccine?

Clotting events are still so rare that it is very difficult to identify any particular risk factors. Although it seems that a marginally higher number of women have experienced clotting, the number of instances isn’t big enough to accurately assess whether gender might affect risk.

The AstraZeneca vaccine isn’t recommended for people that have had a previous case of heparin-induced thrombocytopenia, or of rare cerebral venous sinus thrombosis clots. A family history of clotting doesn’t seem to be related to vaccine dangers since the mechanics are completely different.

Dawn ME Bowdish, Canada Research Chair in Aging & Immunity, McMaster University and Ishac Nazy, Associate Professor of Medicine and Scientific Director of McMaster Platelet Immunology Laboratory, McMaster University

This article is republished from The Conversation under a Creative Commons license. Read the first article.

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