Family Healthcast: How effective is each dose of the COVID-19 vaccine?

Family Healthcast

(WSYR-TV) — As thousands of Central New Yorkers are now fully vaccinated against COVID-19, many more are waiting for their first shot.

We have a question about the effectiveness of each dose:

“How long does it take to get protection from shot number one and when does the full protection kick in from the second dose?”

According to data from more than half a million people who received the first dose of the Pfizer vaccine, new infections actually increased until day eight.

Researchers think that may have been caused by vaccinated people being less cautious.

It actually took two weeks to receive any significant level of immunity. But after day 14, effectiveness increased daily, levelling out at about 51% reduction in confirmed infections three weeks later. This was just in time for the second shot.

With the second dose, there is more data. 1.7 million people who received both doses of the Pfizer vaccine, the vaccine’s effectiveness in preventing severe disease was in the range of 87% to 96%.

Preventing any level of disease, including symptomatic, the range was 66% to 85%.

This shows that a significant number of infections can still occur, although few will be severe. Vaccine effectiveness was somewhat greater among those younger than 60.

What about those more contagious variants that are now spreading here in the United States? Well, there is good and bad news.

A brand new study shows both the Pfizer and Moderna vaccines appear to be highly effective against the variant first detected in Britain.

But, the vaccines showed a decreased ability to neutralize the strain now dominant in South Africa, worrying some researchers and prompting Pfizer to announced they are taking necessary steps to develop a booster shot or updated vaccine.

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