Hi guys.

I just wanted to put a quick thread out here about a concern I'm seeing a lot today re vaccines for COVID-19 and their potential for long-term effects.

I have a more detailed post on my blog here but I can give you the cliff-notes. https://www.deplatformdisease.com/blog/long-term-effects-of-covid-19-vaccines-should-you-be-worried

I get why people have this concern, so let's take a look.

For almost every vaccine we have, there is no such thing as a long-term adverse effect that appears only years after the initial vaccination. If you examine the exception it's easy to understand why.

Varicella vaccines contain a live-attenuated varicella zoster virus. It's the same virus that causes chickenpox, shingles, and all the other fun stuff that varicella does, but the strain (called Oka) is adapted to be unable to grow effectively inside human cells.

The outcome of vaccination is that the immune system gets all the information it needs to be able to defend against infection, and even though you have the varicella virus in you, it doesn't cause disease. Because varicella can't establish an infection, you also avoid shingles.

Still, some people who get this vaccine might develop shingles from the Oka strain years down the line. This is rare. It's also much more likely to happen from the Zostavax vaccine, which elderly people get to prevent shingles, rather than childhood varicella vaccines.

Varicella causes shingles when your immune system weakens (which can happen from any number of things) and reactivates from latency inside your nerves.

Despite the deservedly fearsome reputation of shingles, the cases from the vaccine tend to be much milder, likely because it's still a weakened virus. And you are still MUCH more likely to get shingles from a past chickenpox infection (about 30%) so it's very much worth getting.

The ability of a vaccine to cause these effects years down the line depends on 2 things:

1) The use of a live-attenuated vaccine
2) The ability of varicella viruses, being herpesviruses, to cause persistent infection

Neither of these things alone are sufficient.

The vaccines for COVID-19/SARS-CoV-2 currently in phase 3 do not meet either of these conditions.

mRNA vaccines have a lifetime of maybe a few hours (at most) inside your cells, after which enzymes inside your own cells destroy them.

The Oxford/AZ vaccine is a vectored vaccine, which is live. But unlike the varicella vaccine, the vector is replication-deficient. It cannot make copies, it's just a delivery vehicle for SARS-CoV-2 antigens. Thus no potential for persistent infection.

Taken together, these things suggest that concerns about some latent, long-term consequence of these vaccines are vastly overstated. We have every reason to believe that these vaccines will be safe and effective, and in a pandemic, we can't always have perfect information.

It would be excellent if we could track the study participants for years- and we are. Even though the mRNA vaccines have met their efficacy endpoints and are filing for EUA, participants will be followed for 2 years to document any potential issues related to the vaccine.

But right now there are people being sickened by COVID-19, dying, and facing profound disability and our healthcare system is stretched very thin.

These concerns don't have a good scientific basis, and right now, waiting longer than necessary to validate them is a big risk.

Over 70,000 people have received mRNA vaccines for COVID-19 at this point and there have been no serious adverse events.

There is every reason to believe these are safe vaccines, and while I'd love detailed data, they seem to be very efficacious.

I trust that the experts at the FDA, ACIP, VRBPAC, and the numerous regulatory bodies around the world understand the gravity of the situation and will make the best decision.

But I know that I'm getting the first approved COVID-19 vaccine as soon as I can.

I made a small error in this thread, which I corrected- https://twitter.com/ENirenberg/status/1333918727872589824?s=20