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COVID-19 vaccine efficacy has dropped, says CDC study

A new Centers for Disease Control study shows that as the delta variant became the dominant strain effectiveness of the vaccine dropped from 91% to 66%.

COLORADO, USA — A new study released by the Centers for Disease Control this week, showed that as the delta variant became the dominant strain of COVID in the U.S., the overall vaccine effectiveness dropped from 91% to 66%.

9Health expert Dr. Payal Kohli explained the reason behind the decrease in efficacy and why it is still important to get vaccinated. 

Why has the vaccine efficacy dropped?

Dr. Kohli: Vaccine efficacy does not occur in a bubble but there’s many different factors that go into how well a vaccine works. So the first and most important is your immune response, which we know with the mRna vaccines and the Johnson and Johnson, starts to go down over time. So the longer that it is from the time you were vaccinated the more decline in those neutralizing antibodies you might have and the less effective that vaccine becomes.

The second piece of this is vaccine efficacy depends on how much infection there is in the community. So when there’s a lot of infection around those vaccines, the armor of the vaccines doesn’t work as well. When there’s less infection around, their efficacy tends to go up.

The third [reason] is what type of infection there is in the community. So if it’s the more contagious Delta variant, which you know infects an average of 5 to 9 other people, it's just better at escaping your immune system and better at sticking to your cells. So even if the vaccines are functioning exactly the same, this variant is so much more aggressive that it makes the clinical effectiveness of the vaccines go down.

Is the vaccine still worth getting?

Dr. Kohli: Absolutely because then [the virus] won’t have a chance to mutate and make new variants because we put up an iron wall, we prevent it from mutating inside of us and passing it on to somebody else. So getting vaccinated doesn’t just protect you it actually protects others around you because you’re less likely to catch the infection therefore you’re less likely to spread it. 

It is incredible at keeping you out of the hospital so if you’re vaccinated it reduces your rate of infection by about five-fold and it reduces your chance at ending up at the hospital by about 29-fold and so in the worse case scenario even if you were to get an infection it’s likely to be very mild and highly unlikely to end you up in the hospital so that’s another reason so protect yourself because this is going to keep you from getting sick or from dying.

Now that the vaccine has full FDA approval, I hope that Americans will feel confident in our regulatory process and know that we have tons and tons of data which we’re basing this decision and recommendation to really ask you to get vaccinated to protect yourself but also to protect those around you.

With the drop in efficacy, does that make booster shots even more important? 

Dr. Kohli: This really does raise the question for booster shots because we’re seeing two things happen. The way that we know we need booster shots is the rate of breakthrough infections starts to go up. So we start to see fully vaccinated people having more and more infections, which we’re seeing in some places can be as high as 50% depending on how much infection is in the community, so that’s what really alerted us that now is the time.

Our opponent is getting stronger and our immunity is getting weaker so this is the sweet spot for when we may want to boost our immune system to really make sure we continue to fight, especially that Delta variant.

What is you message to those that are vaccine hesitant and read this study?

I would say be really careful not to take this out of context because this doesn’t necessarily mean the vaccines don’t work. It means they worked and they worked so well that over time that immunity goes down. It also means that our opponent is getting stronger so all the more reason to go out there and get that vaccine because in the face of a mightier opponent the only defense that we have right now, the only defense that we have is to get vaccinated because that’s our best bet in ending the pandemic is protecting ourselves.

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