COVID-19 vaccine

A vaccine helps your body fight a germ.

Some vaccines use a tiny piece of code. This code teaches your body to see a germ.

Your body learns to fight the germ. This helps you stay well. It can stop you from getting very sick.

Some people feel tired or sore after. This goes away in a few days.

Scientists made these vaccines very fast. They help keep many people safe.

A COVID-19 vaccine helps your body fight a virus. This virus causes a sickness called COVID-19.

Vaccines help stop people from getting very sick. They also help prevent death from the virus.

Scientists use different ways to make these vaccines. Some use mRNA. mRNA is a tiny piece of code. This code tells your cells how to make a protein. This protein looks like a part of the virus.

Your body sees this protein and learns to fight it.

Other vaccines use a viral vector. A vector is a tool that carries something. These use a harmless virus to carry the code. This virus is changed so it cannot make you sick.

Some vaccines use a subunit. This means they only use a small part of the virus. One type uses an inactivated virus. This is a virus that has been killed by heat or chemicals.

Some people feel tired or sore after a shot. This usually goes away in a few days. Vaccines are safe for people who are pregnant.

A COVID-19 vaccine is a tool used to protect people from a virus called SARS-CoV-2. This virus is responsible for a disease known as COVID-19. Vaccines are very important because they help reduce the risk of severe illness. They also help prevent people from needing to stay in a hospital. Most importantly, they help prevent death from the virus.

Scientists worked at an unprecedented pace to create these vaccines. They wanted to tackle the global pandemic as quickly as possible.

Different vaccines work in different ways to teach the body to fight. One way is using mRNA, which is a molecule that acts like a set of instructions. These instructions are wrapped in tiny fat bubbles called lipid nanoparticles. Once inside your cells, the mRNA tells the cells to make a specific protein from the virus. This protein is the spike protein, which is the part the virus uses to enter cells.

Your immune system sees this protein and learns how to destroy it. Other vaccines use a viral vector, which is a harmless virus used as a carrier. This carrier is modified so it cannot make you sick or make copies of itself. It only delivers the instructions to make the virus protein.

Scientists did not start from zero in early 2020. They used what they learned from studying other coronaviruses. These included the viruses that cause SARS and MERS. Research on these older viruses helped speed up the work for COVID-19. In fact, Moderna had already begun testing an mRNA vaccine in humans back in 2015. Many scientists had also spent decades studying how mRNA works in mice.

There are several major vaccines that people use around the world. The Pfizer–BioNTech and Moderna vaccines both use mRNA technology. Another example is the Novavax vaccine, which is a subunit vaccine. Subunit vaccines use only a small part of the virus, like a protein, instead of the whole thing.

Some vaccines, like the inactivated virus types, use a virus that has been killed by heat or chemicals. By December 2020, more than 10 billion doses of vaccines had been preordered. Since then, over 13 billion doses have been given to people worldwide.

Getting a vaccine can sometimes make you feel a little bit different for a short time. Common side effects include soreness, fatigue, or a headache. Some people might also feel muscle pain or joint pain. These feelings usually go away on their own within a few days. It is also safe for people who are pregnant or breastfeeding to get the vaccine. As new versions of the virus appear, scientists create updated booster doses. These boosters help maintain protection as immunity from the first shots fades over time.

A COVID-19 vaccine is a medical tool designed to induce immunity against SARS-CoV-2. This specific virus is the pathogen responsible for the disease known as COVID-19. The primary goal of vaccination is to reduce the risk of severe illness, hospitalization, and death. Scientists developed these vaccines at an unprecedented pace to address the global pandemic. The first clinical trials for these vaccines began in March 2020.

Vaccine development relies on several different technological platforms. One major category is mRNA vaccines, such as those from Pfizer–BioNTech and Moderna. These vaccines use messenger RNA, or mRNA, to provide instructions to human cells. The mRNA is encapsulated in lipid nanoparticles, which are tiny fat bubbles. These bubbles protect the mRNA and help it enter the cells. Once inside, the cells express the SARS-CoV-2 spike protein. The spike protein is the part the virus uses to enter human cells.

Another method uses viral vector technology. This approach uses a modified version of a different virus, such as an adenovirus. Scientists make the carrier virus harmless by removing genes that cause illness or replication. They then add DNA that encodes the SARS-CoV-2 spike protein. This allows the vaccine to produce the antigen without making new copies of the carrier virus. Examples of these vaccines include the Oxford–AstraZeneca and Janssen vaccines. Unlike mRNA vaccines, some viral vector vaccines can be stored in a standard refrigerator.

Other platforms include inactivated virus and subunit vaccines. Inactivated vaccines use virus particles that have been killed by heat or formaldehyde. This process removes the ability to cause disease while keeping the structure intact. However, this method can be less efficient because the spike protein may change slightly. Subunit vaccines, like the Novavax vaccine, present only specific parts of the virus. These antigens are often protein subunits rather than whole pathogen particles.

Development was accelerated by significant prior research. Scientists had already studied other coronaviruses, such as SARS and MERS. Research into Middle East respiratory syndrome (MERS) provided a useful template for COVID-19 work. For instance, Moderna began human testing of mRNA technology in 2015. Scientists like Katalin Karikó and Drew Weissman spent decades studying mRNA in mice. Their work was so impactful that they received the 2023 Nobel Prize in Physiology or Medicine.

Global distribution has been massive in scale. By December 2020, more than 10 billion vaccine doses had been preordered. Since then, over 13 billion doses have been administered to people worldwide. Many countries used phased distribution plans to protect the most vulnerable. They prioritized the elderly and healthcare workers who faced high exposure risks. High-income countries purchased about half of the preordered doses, even though they represent only 14% of the world's population.

Vaccination is a dynamic process that changes with the virus. As new SARS-CoV-2 variants emerge, original vaccines are updated. These are often called variant-adapted vaccines and are given as booster doses. Boosters are also necessary because immunity from the initial vaccines can wane over time. While some people experience side effects like fatigue, headache, or muscle pain, these usually resolve quickly. Vaccination remains a safe option for people who are pregnant or breastfeeding.