Covid Vaccine: 6 Things You Need to Know About the Results

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News about clinical trials of Covid-19 vaccines are making headlines. But what do these results really mean? Here are six questions to ask yourself to fully understand.

As the second wave of Covid-19 intensifies in the world, pharmaceutical companies have announced the results of their vaccine trials, which promise to ease restrictions and return us soon to a "normal" life next year.

However, there is a lot of skepticism about vaccines and many question the reliability of these advertisements.

The reluctance to get vaccinated against Covid-19 decreases as people learn more about the safety of vaccines. Therefore, this information is important for making informed decisions in terms of public health.

Here are six questions we can ask ourselves about the announced results of the Covid-19 vaccine trials.

1. What is the test?

The 11 different Phase 3 clinical trials for COVID-19 vaccine candidates each involve thousands of participants receiving a vaccine or a placebo, without knowing which. The researchers then compare the number of infected people who received the vaccine with the number of infected people who received the placebo.

The first results were announced by Pfizer / BioNTech and Moderna. These companies have produced vaccines based on a new technology called messenger RNA (mRNA), which consists of injecting cells with the genetic "recipe" for a fragment of the SARS-CoV-2 protein through a lipid nanoparticle.

Cells use these "instructions" to make pieces of the virus that the immune system will learn to destroy. If approved, this is already the case in the UK, these vaccines will be the first mRNA vaccines to be licensed.

2. Who participated in the trial?

An effective vaccine must reduce the risk of infection in the most vulnerable populations. Severe cases and deaths from Covid-19 are more numerous in racialized groups, especially in indigenous, black and Latin American populations, people over 65 years of age and people with health problems such as diabetes, kidney disease and obesity. However, the lack of representation of these historically marginalized groups has been a problem for years in clinical trials.

In the Pfizer / BioNTech vaccine study conducted in six countries, 42% of the participants are of Asian, African American, Hispanic or Indian descent.

Of the 30,000 participants in Modernas trial, 37% are from racialized groups and ethnic minorities, and the study included a significant representation of people 65 and older and people with high-risk medical conditions.

3. Did the vaccine reduce infections?

The best vaccines protected 95% of the participants from infection, as did the measles vaccines. In comparison, the flu vaccine reduces the risk of infection by about 50%.

Pfizer and BioNTech reported a 90% efficacy rate for the first time after 94 confirmed cases of infection. The trial ended after 170 confirmed cases and an efficacy of 95% for people who received the vaccine and 94% for people older than 65 years.

Modernas vaccine showed an efficacy rate of 94.5%. Of 95 people infected with symptoms, only five were vaccinated.

Like the Pfizer / BioNTech and Moderna vaccines, the Oxford and AstraZeneca vaccine requires a starting dose and a booster dose. The 23,000 participants were expected to receive a control vaccine or a Covid vaccine, as well as a booster.

However, due to a miscalculation, a quarter of the participants who received the Covid vaccine received a half dose followed by a full booster dose. In participants who received two full doses, the vaccine was shown to be 62% effective, while in participants who received only half a dose before the booster, the effectiveness rate was 90%.

Because the group that received half the dose is smaller and the participants were younger, this percentage may not accurately reflect the effectiveness of the vaccine. Thus, in the 131 cases of infection observed in the Oxford / AstraZeneca trial, a mean vaccine efficacy of 70% was observed in all volunteers.

The Pfizer / BioNTech and Moderna trials involved participants who showed symptoms of Covid-19 to be evaluated. In the Oxford and AstraZeneca trial, asymptomatic participants were also regularly assessed. Therefore, the different design of the tests makes comparisons difficult. More data is needed before we can say anything about the effectiveness of vaccines in reducing the number of cases to symptomatic and their potential to transmit the virus.

4. Did the vaccine reduce complications?

It is difficult for a Covid-19 related clinical trial to prove a reduction in severe cases because severe cases are rarer and participants in clinical trials are generally in good health.

Pfizer and BioNTech have yet to provide information on the severity of the cases detected. During Modernas trial, 11 serious infections occurred in people who had not received the vaccine. In the case of the Oxford and AstraZeneca vaccine, none of the 131 reported cases was serious. Even after these trials are over, there is not enough data to say that any of these vaccines prevent serious complications.

5. Is the vaccine safe?

Any vaccine that could cause serious side effects in more than 10% of the hundreds of participants in Phase 2 could not progress to Phase 3. This means that the most common serious side effects, such as allergic reactions requiring hospitalization, are unlikely. .

Most vaccines, including many Covid-19 candidate vaccines, include additives called adjuvants, which produce a stronger immune response, thus providing more effective and long-lasting protection. However, vaccines that contain adjuvants are also more likely to cause reactions such as swelling and fever at the injection site.

6. What are the other considerations?

If multiple vaccines are safe and effective, we can take into account other factors that affect the distribution and access to immunization. Results so far have required two doses per person, requiring more vaccine production and follow-up appointments, which can be a barrier in disadvantaged communities.

Some vaccines also require special shipping and storage precautions. The Pfizer and BioNTech vaccine should be stored at -70 degrees Celsius, a cooler temperature than most clinics and pharmacies can provide. It can be stored for up to five days in the refrigerator. Modernas vaccine is stable for six months at -20 degrees Celsius, one month in the refrigerator, and up to 12 hours at room temperature. The Oxford and AstraZeneca vaccine, made from a modified adenovirus that causes colds, is stable in the refrigerator for at least six months.

What you will not know

A study conducted over a six-month period cannot tell us how long the vaccine will protect against the virus. This question would arise for any new vaccine, but mRNA vaccines are a new technology, which creates more uncertainty. The Pfizer and BioNTech trial was the largest, with 43,000 participants, but it failed to identify rare side effects, such as those that affect one in 100,000 people. Depending on the severity of the side effects, this could change the game on the benefits of the vaccine versus its risks.

These trials also cannot tell us how willing people will be to get vaccinated once the vaccine is approved. The effectiveness of a vaccine in improving public health depends on the number of people who receive it. And they will more easily accept the vaccine if they understand the testing process that led to its approval.

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