How do vaccines work?
Around the world, vaccines save millions of lives each year. Vaccines work by training and preparing the body’s natural defenses --- the immune system--- to recognise and fight off the viruses and bacteria they target. If the body is exposed to those disease-causing germs later, the body is immediately ready to destroy them, preventing illness.
Vaccines stimulate the human body’s own protective immune responses so that, if a person is infected with a pathogen (a micro-organism that can cause disease), the immune system can quickly prevent the infection from spreading within the body and causing disease. In this way, vaccines mimic natural infection but without actually causing a person to become sick.
For more information, please visit: https://www.who.int/news-room/featurestories/detail/how-do-vaccines-work 
What do I need to know about the AstraZeneca vaccine?
How does the AstraZeneca vaccine work?
The AstraZeneca vaccine works by delivering the genetic code of the SARS-CoV-2 spike protein to the body’s cells. Once inside the body, the spike protein is produced, causing the immune system to recognise it and initiate an immune response. This means that if the body later encounters the spike protein of the coronavirus, the immune system will recognise it and destroy it before causing infection. This will help to protect you against COVID-19 in the future. None of the ingredients in this vaccine can cause COVID-19.
This type of vaccine technology has been tested for many other diseases such as influenza (flu) and middle east respiratory syndrome (MERS), another type of coronavirus.
AstraZeneca’s COVID-19 vaccine is 76% effective against symptomatic coronavirus infections and 100% effective in preventing hospitalization and severe disease, according to an interim analysis of its United States phase 3 trial, which included more than 32,000 people.
Even better, AstraZeneca’s vaccine can be stored at normal refrigerator temperatures, meaning it could be key to reaching people in rural and underfunded areas, one of the most pressing issues in the fight against the coronavirus.
Is the Vaccine Safe?
The AstraZeneca vaccine has been given authorisation by the UK Department of Health and Social Care and the Medicines and Healthcare products Regulatory Agency.
The vaccine has also been approved by several medicine agencies worldwide, such as the European Medicines Agency (EMA), and the Australian Therapeutic Goods Administration, and was approved for an Emergency Use Listing by the World Health Organization (WHO)
What you need to know before you receive the AstraZeneca Vaccine
Talk to your doctor, pharmacist or nurse before taking AstraZeneca if you have had any of the following:
- If you have ever had a severe allergic reaction (anaphylaxis) after any other vaccine injection;
- If you currently have a severe infection with a high temperature (over 38°C).
- If you have a problem with bleeding or bruising, or if you are taking a blood thinning medicine (anticoagulant);
- If your immune system does not work properly (immunodeficiency) or you are taking medicines that weaken the immune system (such as high-dose corticosteroids, immunosuppressants or cancer medicines).
- If you have ever had a blood clot in the sinus veins in the brain, or the autoimmune condition called antiphospholipid syndrome.
Extremely rare cases of blood clots with low levels of platelets have been observed following vaccination with COVID-19 Vaccine AstraZeneca. The majority of these cases occurred within the first 14 days following vaccination but some have also been reported after this period. Some cases were life-threatening or had a fatal outcome. It is important to remember the benefits of vaccination to give protection against COVID-19 still outweigh any potential risks.
If you experience any of the following from around 4 days after vaccination you should seek medical advice urgently:
- A severe headache that is not relieved with simple painkillers or is getting worse or feels worse when you lie down or bend over
- An unusual headache that may be accompanied by blurred vision, confusion, difficulty with speech, weakness, drowsiness or seizures (fits)
- Rash that looks like small bruises or bleeding under the skin beyond the injection site
- Shortness of breath, chest pain, leg swelling or persistent abdominal (tummy) pain.
Tell your doctor, pharmacist or nurse if you experienced a blood clot occurring at the same time as low levels of platelets after receiving a previous dose of a COVID-19 vaccine.
As with any vaccine, COVID 19 Vaccine AstraZeneca may not protect everyone who is vaccinated from COVID-19. It is not yet known how long people who receive the vaccine will be protected for. No data are currently available in individuals with a weakened immune system or who are taking chronic treatment that suppresses or prevents immune responses.
Pregnancy and breastfeeding
If you are pregnant or breastfeeding, think you may be pregnant, or are planning to have a baby, tell your doctor, pharmacist or nurse. There are limited data on the use of COVID-19 Vaccine AstraZeneca in pregnant or breastfeeding women. Your doctor, pharmacist or nurse will discuss with you whether you can be given the vaccine.
Driving and using machines
COVID-19 Vaccine AstraZeneca has no known effect on the ability to drive and use machines. However, side effects may impact your ability to drive and use machines. If you feel unwell, do not drive or use machines.
How COVID-19 Vaccine AstraZeneca is given
The AstraZeneca Vaccine is injected into a muscle (usually in the upper arm).
You will receive 2 injections and you will be told when you need to return for your second injection.
The second injection can be given between 4 and 12 weeks after the first injection.
Will I have to get both shots of the vaccine?
It is important to note that both doses are required (two shots, given at least four weeks apart) for the vaccine to be effective. The first dose of the vaccine acts as a primer to begin building protection against Covid-19 disease. The second dose is believed to increase this level of protection and provide longer term protection. It is important to ensure you receive both doses to obtain the full amount of protection the vaccine can provide.
Possible side effects
Like all medicines, this vaccine can cause side effects, although not everybody gets them. In clinical studies with the vaccine, most side effects were mild to moderate in nature and resolved within a few days with some still present a week after vaccination.
If the side effects such as pain and/or fever are troublesome, medicines containing paracetamol can be taken.
Common side effects that occurred during clinical trials with the AstraZeneca Vaccine were as follows:
- Tenderness, pain, warmth, itching or bruising where the injection is given
- Generally feeling unwell
- Feeling tired (fatigue)
- Chills or feeling feverish
- Feeling sick (nausea)
- Joint pain or muscle ache
- Swelling, redness or a lump at the injection site
- Being sick (vomiting) or diarrhoea
- Flu-like symptoms, such as high temperature, sore throat, runny nose, cough and chills
Less common side effects reported during the clinical trials included:
- Feeling dizzy
- Decreased appetite
- Abdominal pain
- Enlarged lymph nodes
- Excessive sweating, itchy skin or rash
Some people have reported a sudden feeling of cold with shivering/shaking accompanied by a rise in temperature, possibly with sweating, headache (including migraine-like headaches), nausea, muscle aches and feeling unwell, starting within a day of having the vaccine and usually lasting for a day or two.
If your fever is high and lasts longer than two or three days, or you have other persistent symptoms, this might not be due to side effects of the vaccine and you should follow appropriate advice according to your symptoms.
In clinical trials there were very rare reports of events associated with inflammation of the nervous system, which may cause numbness, pins and needles, and/or loss of feeling. However, it is not confirmed whether these events were due to the vaccine.
Following widespread use of the vaccine there have been extremely rare reports of blood clots occurring with low levels of platelets. There is a risk of developing blood clots from Covid-19 disease, which is far greater than the risk of developing blood clots from the vaccine. In performing a benefit vs risk analysis, in most cases the outcome will be it is safe for individuals to receive the vaccine, rather than risk contracting Covid-19 disease.
The future for AstraZeneca
“The next generation of vaccines, like AstraZeneca’s, which is kept at refrigerator temperatures, is a major advancement,” says Kawsar Talaat, M.D, an infectious disease doctor, vaccine researcher, and assistant professor in the department of International Health at Johns Hopkins University. “When you’re talking about distribution to the entire world, it’s much easier to do because we already keep vaccines cold. It’s a lot harder to keep things frozen.”
Remember: Vaccines are an important tool in our fight against Covid-19, but, they must be combined with masks, hand-washing, and social distancing to help end the pandemic.
Click here to learn about the Pfizer-BioNTech vaccine.
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