Types of Covid Vaccines: How They Work, Effectiveness, & Side Effects – Healthline

Vaccines have been a critical tool in managing the COVID-19 pandemic. Researchers have been working on vaccines against the novel coronavirus, known as SARS-CoV-2, since it was first identified and characterized.

In fact, the World Health Organization (WHO) estimated that more than 200 COVID-19 vaccine candidates were in development in December of 2020. Since then, several vaccines have been authorized or approved for use around the world.

Generally speaking, there are four different types of COVID-19 vaccines that are being used throughout the world. Keep reading to learn what these are, how they work, and more.

As just mentioned, there are four types of COVID-19 vaccines that are being used around the world. These are:

The table below provides a brief summary of the different types of COVID-19 vaccines and the branded names that theyre associated with.

The mRNA vaccines work by teaching your body to make a protein from the novel coronavirus. This protein is called the spike protein. Normally, the virus uses it to attach to and enter cells.

These vaccines contain a molecule called mRNA thats surrounded by a protective lipid (fat) layer. The function of mRNA is to tell cells how to make proteins. Your cells use mRNA every day to make proteins that are vital for life.

Heres how the mRNA vaccines work:

There are currently two mRNA vaccines in use. These are the Pfizer-BioNTech and Moderna vaccines. Both of these vaccines are given as two doses. The Pfizer-BioNTech does are spaced out over 21 days (3 weeks). The Moderna doses are spaced out over 28 days (4 weeks).

Large-scale clinical trials found that both mRNA vaccines were very effective. Vaccine effectiveness was found to be 95 percent and 94.1 percent for the Pfizer and Moderna vaccines, in that order.

However, much has changed since these trials. Variants of the novel coronavirus have emerged, such as the highly infectious Omicron variant. The mRNA vaccines are less effective against these variants.

Because of the rise of variants as well as naturally decreasing immunity, public health organizations around the world have recommended booster doses.

As a result, research has focused on vaccine effectiveness in terms of variants and booster doses. Lets see what some of this research says.

A 2022 study examined the effectiveness of the Pfizer vaccine between November 2021 and January 2022. This studys findings about the effectiveness against the Omicron variant were as follows:

Another 2022 study looked at the effectiveness of the Moderna vaccine against the Omicron variant. This study reported the following:

Viral vector vaccines for COVID-19 use a modified virus to deliver instructions to your cells on how to make the spike protein. The modified virus is harmless and cant make copies of itself or cause disease.

The viral vector vaccines for COVID-19 all use an adenovirus vector. In nature, adenoviruses can cause cold- or flu-like symptoms.

Viral vector vaccines work in the following way:

There are a few examples of viral vector vaccines in use throughout the world. These include:

The large-scale clinical trials of the J&J vaccine found that a single vaccine dose was 66.9 percent effective for preventing moderate to severe or critical COVID-19.

Clinical trials of the AstraZeneca vaccine found that overall vaccine effectiveness after two doses was 70.4 percent.

The arrival of the Omicron variant has hit viral vector vaccines pretty hard. However, receiving a booster with an mRNA vaccine can help.

One of the 2022 studies discussed earlier also looked at the effectiveness of the AstraZeneca vaccine against the Omicron variant. This studys findings were as follows:

Protein subunit vaccines are pretty straightforward. They contain a purified protein from a virus that the immune system can see and respond to. In the case of the novel coronavirus, this protein is the spike protein.

Protein subunit vaccines work in the following way:

There are various protein subunit vaccines in development. One that you may have heard of is the Novavax vaccine, which is given in two doses spaced 21 days (3 weeks) apart.

The spike protein in the Novavax vaccine is made in cells in a laboratory and is purified before being stuck onto a tiny, round particle called a nanoparticle. This design imitates the shape of the novel coronavirus and also helps to group many spike proteins together so that the immune system can see them.

A large-scale clinical trial of the Novavax vaccine found that its effectiveness was 90.4 percent.

However, this trial was performed in early 2021, before the arrival of the Delta and Omicron variants. Detailed data on the Novavax vaccines effectiveness against these variants havent been published yet.

So far, Novavax has released a statement based off of early data that antibodies from the first two-dose vaccine series have some effectiveness against the Omicron variant. Protection also increased after a booster dose.

The last type of COVID-19 vaccines are whole virus vaccines. These vaccines contain whole virus particles, known as virions, of SARS-CoV-2, the virus that causes COVID-19.

The only whole virus vaccines that are in use are inactivated. In an inactivated vaccine, the virus has been treated so that it remains whole but cant cause disease. This is typically accomplished by using chemicals or heat.

An inactivated whole virus vaccine works in the following way:

Two examples of inactivated whole virus vaccines are the Sinovac and Sinopharm vaccines.

A 2021 study of the Sinovac vaccine, called CoronaVac, found that vaccine was only 46.8 percent effective against symptomatic SARS-CoV-2 infection after the second vaccine dose.

The Omicron variant has greatly impacted the effectiveness of the available inactivated vaccines.

Overall, researchers are finding that these vaccines provide little to no protection against this variant. However, boosters with another type of vaccine may help to restore this protection.

Before being used on a wide scale, all vaccines need to be shown to be both safe and effective in large-scale clinical trials.

In the United States, the Food and Drug Administration (FDA) reviews the data from these trials before approving the vaccine or issuing an emergency use authorization.

Generally speaking, some of the most common side effects of COVID-19 vaccines are:

These side effects typically come on within a day of receiving a vaccine dose. They only last a few days before going away on their own.

If you have side effects such as fatigue, fever, and muscle pain, you may feel as if the vaccine is making you sick. However, these symptoms are completely normal and are actually a sign that your body is creating an immune response to the vaccine.

There are some people who shouldnt receive a COVID-19 vaccine. This is called a contraindication to vaccination. For the vaccines that are currently in use in the United States, the only contraindications to COVID-19 vaccines are:

In rare situations, mRNA vaccines can lead to myocarditis, or inflammation of the heart muscle. The Centers for Disease Control and Prevention (CDC) notes that this is more common:

According to a 2021 study of 139 teens and young adults with suspected myocarditis after vaccination, the condition was typically mild and resolved quickly when treatment was given.

Additionally, a 2022 study found that a person was more likely to develop myocarditis after contracting SARS-CoV-2 than after receiving a COVID-19 vaccine.

Although very rare, serious side effects such as TTS and Guillain-Barr syndrome (GBS) have been reported after vaccination with viral vector vaccines such as the J&J and AstraZeneca vaccines.

Based off of an updated risk-benefit analysis, the CDC is now recommending that people receive an mRNA vaccine over the J&J vaccine. This recommendation was made based on the fact that the J&J vaccine:

Similarly, the United Kingdom offers alternatives to the AstraZeneca vaccine in individuals under the age of 40. These alternatives were offered because people in this age group, particularly people assigned female at birth, are at a higher risk of TTS.

There are several different types of COVID-19 vaccines. These vaccines all work in different ways to prepare your immune system to respond to the novel coronavirus, should you be exposed to it.

Before being widely used, vaccines must go through a rigorous clinical trial process to assess their safety and effectiveness. As such, vaccines that have been authorized or approved have been shown to be safe and effective.

To increase your protection against COVID-19, its important to stay up to date on your COVID-19 vaccinations. Never hesitate to talk with a doctor or other healthcare professional if you have any concerns or questions about vaccination.

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Types of Covid Vaccines: How They Work, Effectiveness, & Side Effects - Healthline