COVID-19 Vaccines FAQs
Vaccines are biological products, often injections, that protect your body from certain infections.
Vaccines prepare your immune system to protect your body from foreign infection-causing pathogens, such as bacteria, viruses, parasites or fungi. Your immune system is the system of cells and tissues that protects your body from infection.
Vaccines help your immune system “learn” about a pathogen and build a defense that will protect you from getting infected with the same pathogen in the future.
Vaccines have been around for over 200 years. They are considered to be one of the biggest successes in modern medicine and – according to the WHO - only surpassed by clean drinking water in impact on human health globally. The WHO estimates that vaccines currently save about 2 to 3 million lives each year globally.
COVID-19 vaccines train your body’s immune system to defend itself against SARS-CoV-2, the coronavirus that causes COVID-19 illness.
All COVID-19 vaccines contain antigens, or a blueprint to make antigens in the body. Antigens are a part of a pathogen that trigger your immune system to launch a response to fight an infection. Antigens (or the genetic blueprint to make them) in the vaccine help your immune system make antibodies (substances that protect your body against infection) against COVID-19 to protect your body in the future.
Many different COVID-19 vaccines have been authorized for use or are in Phase 3 clinical trials. The WHO has a useful tracker of all COVID-19 vaccine candidates currently being evaluated in clinical trials.
COVID-19 vaccines can contain:
- Weakened or inactive parts of a certain antigen that triggers an immune response within your body.
- The blueprint to make an antigen instead of the antigen itself.
We can divide the most common types of COVID-19 vaccines into four broad groups:
- mRNA vaccines (nucleic acid)
- protein subunit or recombinant protein vaccines.
- non-replicating viral vector vaccines.
- Inactivated or weakened whole virus vaccines
This type of vaccine contains a part of genetic code (RNA) from the virus that causes COVID-19 infection, the SARS-CoV-2 virus. This genetic code or RNA serves as a “blueprint” for an antigen of interest. In this case the mRNA vaccines tell the cells of your body to make a harmless piece of the virus, the “spike protein.” The spike protein is found on the surface of the SARS-CoV-2 virus.
Your immune system then makes antibodies in response to this spike protein. It also creates a memory for this defense response, so your body can more easily recognize & fight off the SARS-CoV-2 virus if you are exposed to it in the future.
The mRNA COVID-19 vaccines use a newer method than traditional vaccines, but researchers have been studying and working with mRNA vaccines for decades. For example, mRNA vaccines have been studied before in clinical trials with thousands of people for flu, Zika, rabies, and cytomegalovirus (CMV), and mRNA-based medicines are also in development.
This type of vaccine contains purified fragments (not the whole virus) of protein from the SARS-CoV-2 virus, which your immune system detects as foreign and to which it responds by making antibodies. Your immune system develops a memory for this response, so your body can more easily recognize and fight off the SARS-CoV-2 virus if you are exposed to it in the future.
Protein subunit vaccines have also been used to develop for example the Hepatitis B vaccine and several other vaccines that are being used routinely today.
This type of vaccine uses an unrelated harmless virus (called the viral vector) to deliver SARS-CoV-2 genetic material or “blueprint” for the antigen into the body. The harmless viral vector has been modified, so it cannot replicate or cause any infection, rather it is simply a way to deliver the antigen into the body. When you get this type of vaccine, your body’s cells use this genetic material within the vector to make the “spike protein” of the SARS-CoV2 virus, without causing an infection. Your immune system then detects the protein as foreign and responds to it by developing antibodies. Your immune system also develops a memory for this response, so your body can more easily recognize and fight off the SARS-CoV-2 virus if you are exposed to it in the future.
Non-replicating viral vector vaccines have been extensively studied for various diseases (for example flu, SARS, MERS), have also been used in the past to develop a vaccine against Ebola and are currently being used in several vaccines in development at the moment.
Whole virus vaccines use an inactivated or weakened (attenuated) form of the virus to trigger an immune response. These types of vaccines are well known and use the most standard approach to developing vaccines.
In the case of inactivated vaccines, scientists inactivate the genetic material of the SARS-CoV-2 virus by using heat, chemicals, or radiation (high energy). This means the genetic materials of the virus is weakened and cannot make copies but can still trigger an immune response.
Your immune system finds and responds to the inactivated virus by developing antibodies, without causing COVID-19 illness. Your immune system also develops memory for this response, so your body can more easily recognize and fight off the SARS-CoV-2 virus if you are exposed to it in the future. Examples of inactivated virus vaccines include vaccines for the seasonal flu, hepatitis A, polio, and rabies.
In the case of attenuated vaccines, the virus is weakened and only makes copies very slowly, so the immune system has more time to overcome the infection than normal. Examples of inactivated virus vaccines include vaccines for measles, mumps, rubella, and chickenpox.
Many of the ingredients in vaccines are naturally found in your body or in food. Sterile water, for example, is one of the main ingredients in many vaccines.
The key ingredient in all vaccines is an active component (the antigen) or a blueprint for making the active component. The antigen may be a tiny part of the disease-causing organism, like a protein or sugar, or it may be the whole organism in a weakened or inactive form. This causes your body to detect the antigen as foreign and triggers an immune response by training your immune system to fight the virus in the future.
The exact composition of each COVID-19 vaccine depends on the type of vaccine and not all COVID-19 vaccines contain the following ingredients. Other ingredients designed to help keep vaccines safe and effective could include:
- Stabilizers: These help a vaccine remain unchanged when the vaccine is exposed to heat, light, acidity, or humidity. For example, sugar is used to protect the mRNA vaccine during freezing.
- Adjuvants: These are substances that create a stronger immune response to the vaccine. They are very useful for vaccines given to older people, who tend to have lower immune responses to vaccines.
- Preservatives: These prevent the vaccine from becoming contaminated once the vial is opened. For example, 2-phenoxyethanol is a commonly used preservative and is also used in a range of baby care products.
- Surfactants: They keep all the ingredients in the vaccine blended together and are also often used in foods like ice-cream.
Vaccines can contain very small amounts of some of the ingredients listed above. Usually, your body or food contains much larger amounts of many of these ingredients than the amount used in a vaccine.
All the ingredients in vaccines are thoroughly tested and assessed by independent regulatory authorities who identify any safety concerns.
For a full list of ingredients in each vaccine, refer to the Patient Information Leaflet (PIL) or Summary of Product Characteristics (SPC) sheet that comes with each vaccine. You can also find these ingredients on vaccine makers’ websites.
When a vaccine is too hot or too cold, it can become less effective or even inactive. If stored at the incorrect temperature, vaccines can be ruined or unsafe for use. Most vaccines require refrigerated storage at between 2 and 8 °C. Some vaccines require temperatures as cold as -20°C. Some of the newer vaccines need to be kept ultra-cold at -70°C.
A vaccine is only authorized or approved for use with the public after health authorities review all the clinical and scientific data from the clinical trials. Once vaccines are authorized or approved for public use, they are continually monitored for safety and that the vaccines work well in different groups of people over time. The health authorities also check for side-effects that may become apparent only in the longer term.
Vaccines are complex biological products. It takes highly skilled people, specialised supplies and facilities, and quality ingredients to make them. They also have to undergo strict safety and quality control measures.
Vaccine makers are required to follow strict quality control procedures on an ongoing basis in the factories where vaccines are made. The manufacturing process requires quality control steps at each stage, with some vaccines having as many as 450 quality checks at each stage. Any possible problems at any point in the process could result in the entire batch being thrown away.
Quality control can take up to 70% of the manufacturing time. Quality is closely watched on a batch-by-batch basis according to standards of manufacturing practice set and checked by health authorities.