Health

What do we really know about the effectiveness of the vaccine?

The politicization of COVID vaccines – and everything else related to the pandemic – has led to confusion, if not complete fatigue.

And some of the posts circulating on social media – like this neatly edited YouTube article – seem to be based on those sentiments, trying to question the effectiveness of vaccines. This commentary is interspersed with comments from White House medical adviser Dr. Anthony Fauci, praising their defensive ability, with screenshots of news headlines, starting with those that cite 100% effectiveness and then progressing to others reporting sharply lower percentages. Set at the skyrocketing pace of the orchestral piece “In the Hall of the Mountain King,” the video ends with headlines on the profits of pharmaceutical companies.

But slowing down the video for headline analysis reveals a lot of complexity. Some report studies that only looked at infection rates; others have more serious outcomes, including hospitalization and death. Some of them are about vaccines that are not offered in the United States.

In short, video contributes to misperceptions by mixing disparate data and missing key details.

However, one cannot help but wonder what actually happens to efficiency – and is there any surprise in that?

If you don’t read further, know that no vaccine is 100% effective against any disease. COVID shots are no exception. The effectiveness of infection prevention, defined as a positive test result, in some studies diminishes sharply as more time passes after the completion of the one- or two-dose regimen. But on key measures – preventing serious illness, hospitalization, and death – real-world studies in the US and abroad tend to show a slight weakening of defenses, especially in older or more sick people, but generally remain strong, even as the more infectious delta grows. variant of the COVID virus.

The essence? Vaccination with any of the three vaccines available in the US primarily reduces the chances of infection and greatly reduces the risk of hospitalization or death if you do become infected with COVID-19. The Centers for Disease Control and Prevention recently published a study showing that fully vaccinated people are more than 10 times less likely to die or be hospitalized than unvaccinated people.

“When it comes to what’s important, vaccines hold up very well,” said Dr. Amesh Adala, an infectious disease physician and senior fellow at the Johns Hopkins Center for Health Security. “They were designed to tame the virus.”

So what do “efficacy” and “efficacy” mean in general?

Before a drug or vaccine gets the green light from federal regulators, it is tested on volunteers who are randomly assigned to receive a product or placebo. The researchers then compare how the groups live. In the case of a vaccine, they look at how well it prevents infection and whether it protects against serious illness, hospitalization, or death. These clinical trial results are often referred to as performance indicators.

In the real world, however, numerous factors influence the effectiveness of a drug or vaccine, including the much larger population receiving it, some of which have underlying conditions or socioeconomic circumstances different from those in clinical trials. This real measure of efficiency is called efficiency.

Pfizer-BioNTech and Moderna, two-dose vaccines, have been shown to be 90% effective against symptomatic diseases after being approved for emergency use following clinical trials. The Johnson & Johnson single-dose shot, which was tested later as more variants became available, showed overall efficacy in the high 60% range. These numbers have exceeded the 50% threshold that health officials were aiming for at least for the effectiveness of the COVID vaccine. Also keep in mind that the actual effectiveness of an annual flu vaccine is often between 40% and 50%.

Another point: 95% effectiveness does not mean that 95% of vaccinated people will never get infected. This means that a fully vaccinated person exposed to the virus only faces a 5% risk of infection compared to an unvaccinated person.

Have performance metrics changed?

Yes, in some studies, there has been a decrease in effectiveness against infections. Some also expressed concern that protection against serious diseases could also be reduced, especially in the elderly and patients with underlying medical conditions.

The reasons for the decline are varied.

First, when vaccines were allowed, much of the United States was under stricter rules for staying at home due to the pandemic. Almost a year later, restrictions, including the rules on the use of masks, have been loosened in many areas. More and more people travel and find themselves in situations that they would have avoided a year ago. So, the exposure to the virus is higher.

Several studies in the United States and abroad show that time since vaccination also plays a role.

The Lancet recently published a study of over 3.4 million Kaiser Permanente members, both vaccinated and unvaccinated, looking at the effectiveness of the Pfizer vaccine. It showed an overall average efficacy of 73% against infection within six months after vaccination and an overall efficacy of 90% against hospitalization.

But protection against infection dropped from 88% one month after full vaccination to 47% after five to six months. The researchers concluded that the time since vaccination played a bigger role than any changes in the virus itself.

“This shows that vaccines are highly effective against severe outcomes over time,” said lead author Sarah Tartof, an epidemiologist with Research and Evaluation, Kaiser Permanente, Southern California. “In terms of infection, it decreases over time, which is not surprising. We have boosters for many other vaccines. ”

The virus also mutated.

“Delta has come, too,” said Dr. William Schaffner, professor of preventive medicine at Vanderbilt University School of Medicine. “Because this virus was so contagious, it changed the results a little.”

And some vaccinated people can become seriously ill with COVID or even die, especially if they have an underlying health problem, as in the case of General Colin Powell. He died of complications from COVID, although he was fully vaccinated – likely because he also had a blood cancer called multiple myeloma, which can reduce the body’s response to an invasion of the virus, as well as to vaccinations.

What should we do with these changing numbers and recent booster vaccinations?

Most scientists, researchers and doctors say vaccines work wonderfully, especially in preventing serious illness or death.

And it is not unusual to need more than one dose.

Both shingles and measles vaccines require two shots, while humans must be boosted against tetanus every 10 years. Because the flu changes every year, flu shots are given annually.

The immune response is often better when vaccines are spread out over several months. But during the introduction of the COVID vaccine, so many people fell ill and died from COVID every day that the FDA and the CDC decided not to delay, but to allow the first and second doses after about a month.

“We learn as we go,” Schaffner said. “It has always been assumed that additional doses may be required.”

The guidelines now call for a second dose for anyone who received the J&J vaccine at least two months before. Those who have received the Pfizer or Moderna two-dose vaccine are advised to wait six months after the second dose to receive a booster, which is currently recommended for those 65 years of age or older; have any of the many underlying medical conditions; live in a collective setting, such as nursing homes; or have a job that puts them at higher risk. Booster recommendations may expand in the coming months.


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