What is it?

COVID-19 disease is caused by an infection with the highly contagious SARS-CoV-2 virus, a type of coronavirus discovered in 2019. The virus spread rapidly and led to a global pandemic. Multiple strains and subvariants of SARS-CoV-2 have since emerged. The different strains and subvariants vary both in the severity of symptoms they cause and how transmissible they are. 

COVID-19 disease has had vast impacts on society. In addition to the public health implications, the economic, social and mental health effects have been and continue to be significant.  

What to look for?

Infections can be asymptomatic or can result in a spectrum of symptoms, from mild respiratory symptoms to more serious disease affecting multiple organs and systems. Severe disease can lead to hospitalisation, mechanical ventilation, and can be fatal.   

Common symptoms of acute COVID-19 infection can include fever, cough, myalgia (body aches), dyspnoea (difficulty breathing), gastrointestinal symptoms (e.g., diarrhoea, nausea or vomiting), headache, sore throat, loss of smell or taste, and rhinorrhoea (runny nose).   

Some individuals can experience ongoing symptoms for weeks or months after their initial diagnosis, known as long COVID or post-COVID conditions. Symptoms can include extreme fatigue, post-exertional malaise, dyspnoea , chest pain, heart palpitations, fever, arthralgia (joint pain), paresthesia (pins and needles), rash, hoarse voice, problems with memory and concentration (brain fog), sleep problems, changes with taste or smell, gastrointestinal symptoms, changes in menstrual cycles, weight loss and poor appetite, mood changes (depression, anxiety), and difficulty completing activities of daily living. In addition, long COVID can have a huge impact on an individual’s quality of life, mental health and ability to participate in work or schooling. Long COVID is more common in people who have experienced severe COVID-19 disease, those who had underlying medical conditions prior to infection (e.g. hypertension, chronic lung disease, diabetes, obesity) and those who are unvaccinated. 

Paediatric Multisystem Inflammatory Syndrome Temporally associated with SARS-CoV-2 (PIMS-TS), or Multisystem Inflammatory Syndrome in Children associated with COVID-19 (MIS-C), is a newly described condition that has been reported in children in the first 2-6 weeks after COVID-19 infection. It is an inflammatory condition, similar to Kawasaki disease, and is characterised by rash, fever, shock and abdominal pain. Children experiencing PIMS-TS almost always require hospitalisation for treatment.

How is it transmitted?

COVID-19 is transmitted through the inhalation of virus particles made airborne when an infected person coughs, sneezes, breathes, speaks or sings. Droplets containing virus particles can contaminate surfaces and can be spread when a person touches these surfaces and then touches their nose, mouth or eyes. Poorly ventilated settings can also contribute to the spread of COVID-19 because aerosol particles can remain suspended in the air for several hours longer than in well-ventilated settings (minutes to hours). 

The incubation period for the disease is 1 to 14 days, with most individuals displaying symptoms 5 to 6 days after being exposed. Individuals are most infectious in the 2 days before their symptoms begin and the early stages of their illness. People with asymptomatic disease can still infect others.   


Since 2019, over 770 million infections have been reported worldwide contributing to almost 7 million deaths, with true figures likely to be much higher. 

Individuals with immunocompromise, advancing age (particularly > 70 years), obesity, respiratory conditions, pregnancy, heart disease, diabetes, renal disease, liver disease, neurological conditions and disability are more likely to experience severe symptoms if infected with SARS-CoV-2. 

Certain occupations, such as working in healthcare, increase likelihood of exposure to SARS-CoV-2 and therefore infection.  

Repeat infections can occur.  


Strategies to reduce risk of transmission of COVID-19 disease include standard precautions such as hand hygiene, wearing masks when remaining socially distant is not possible and ensuring indoor spaces have good ventilation.  

Vaccination aims to reduce the severity of COVID-19 symptoms and the need for hospitalisation. There are 3 vaccine brands available for use within Australia: 

  • Comirnaty (Pfizer) vaccine containing nucleoside-modified mRNA encoding the spike glycoprotein of SARS-CoV-2   
  • Spikevax (Moderna) vaccine containing nucleoside-modified mRNA encoding the spike glycoprotein of SARS-CoV-2   
  • Nuvaxovid (Novavax) vaccine containing SARS-CoV-2 spike glycoprotein, adjuvanted with Matrix-M.

Of these vaccine brands, there are alternatives based on which strain or subvariant of SARS-CoV-2 they target and different strength formulations for different age groups. Monovalent vaccines target a single strain, whereas bivalent vaccines target 2 strains.  

The first COVID-19 vaccines targeted the ancestral strain of the SARS-CoV-2 virus. Newer vaccines target the strains that are now circulating. While the SARS-CoV-2 virus continues to mutate, new vaccines are likely to be on the horizon.  

All COVID-19 vaccines provide protection against severe COVID-19 symptoms. However, vaccines targeting the current circulating strains are preferentially recommended (if available for use in that age group).  

Primary course

A primary course of vaccination is recommended for all individuals from 5 years of age. Immunocompetent individuals (those with a functioning immune system) should receive 2 doses, 8 weeks apart. Those with immunocompromise should receive 3 doses, with 8 weeks between each dose.

Children aged 6 months to ≤ 4 years with severe immunocompromise, certain disabilities and those who have complex and/or multiple health conditions which increase the risk of severe COVID-19 should also receive a primary course of COVID-19 vaccination. In this age group, a primary course consists of 3 doses with 8 weeks between each dose, regardless of immune function (refer to table below for ageappropriate vaccine). 

Booster doses

Recommendations for booster doses vary depending on the age of the individual and their risk factors for severe disease. An interval of at least 6 months since a confirmed COVID-19 infection/previous booster or primary course is recommended before administering a booster dose. Booster doses are not recommended for anyone less than 5 years of age. 

 For recommendations on COVID-19 booster doses, see ATAGI advice on boosters (last updated in September 2023). 

Vaccines brands and type available for use by age group

WordPress Tables Plugin

shaded boxes indicate preferred vaccine type used in each age group.
shaded boxes indicate that vaccine is not available for use in this age group.
 shaded boxes indicate newly available vaccines (from December 2023).

Side effects following vaccination

Common side effects 

Most side effects following COVID-19 vaccination are mild and can include pain at the injection site, fatigue, headache, lymphadenopathy and fever. 

Rare side effects  

Myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining around the heart) are rare conditions that have been reported following administration of COVID-19 vaccines. They are most commonly associated with viral infections (including COVID-19 disease) but can also be triggered by other factors such as medications and autoimmune conditions. In the setting of vaccination, the peak risk group for myocarditis is young adult males aged between 16 and 24 years following a second dose of vaccination. Pericarditis occurring after vaccination is more common in the 20 to 45 year old age group for both males and females. 

Thrombosis with thrombocytopenia (TTS) was a rare condition that was reported to occur in people who had previously received the COVID-19 vaccine Vaxzevria (AstraZeneca). Since March 2023, Vaxzevria is no longer available for use in Australia.

Commonly asked questions

  • Why are monovalent XBB.1.5 vaccines preferentially recommended?

    All currently available COVID-19 vaccines provide strong protection against severe disease. However, monovalent XBB.1.5 vaccines show a modest increase in protection against the predominant circulating strains. 

  • Can pregnant or breastfeeding women receive COVID-19 vaccines?

    Yes it is safe to administer COVID-19 vaccines at any stage of pregnancy. Due to an increased risk of severe outcomes for pregnant women and their unborn babies it is recommended that pregnant women have received a primary course of COVID-19 vaccination. Administration of booster doses can also be considered if they are due.

    Breastfeeding women can receive COVID-19 vaccines. They do not need to stop breastfeeding before or after being vaccinated.

    Real world surveillance of international data on mRNA COVID-19 vaccine administration in pregnant women has shown no significant safety concerns for either the mother or the baby. Further to this, antibodies have been detected in the cord blood and breastmilk of vaccinated women, suggesting a transfer of protection to the baby.

  • Where can I access COVID-19 vaccines?

    Individuals aged ≥ 5 years can access COVID-19 vaccines through GP clinics and some pharmacies. Children aged 6 months to ≤ 4 years can receive COVID-19 vaccines through hospital immunisation services at Monash Children’s Hospital, the Royal Children’s Hospital and Joan Kirner Women’s and Children’s Hospital (Sunshine). To find your closest provider and make an appointment visit the Health direct website.  

  • What is the recommended interval between COVID-19 infection and vaccination?

    An interval of 6 months between COVID-19 infection and COVID-19 vaccination (primary dose or booster dose) is recommended.

  • Can COVID-19 vaccines be administered on the same day as other vaccines?

    In most instances COVID-19 vaccines can be co-administered (given on the same day) with other vaccines, including influenza vaccines.  

    The only exception to this is for children aged 6 months to < 5 years, where separating COVID-19 vaccines and other vaccines by 7 to 14 days is preferred.  This recommendation aims to minimise adverse events such as fever, which can occur in the 3 days following inactivated vaccines and 7 to 10 days post vaccination with the live-attenuated MMR vaccine.  In children under 5 years, COVID-19 vaccines may be co-administered if separating vaccines would be logistically challenging (e.g. distant travel required to access vaccines, limited days available to attend vaccine appointments). 

  • How do we complete a primary course of vaccination for children < 5 years who started with Spikevax?

    Immunocompetent children who commenced their primary course with 1 dose of Spikevax (Moderna), can complete their primary course with a single dose of age-appropriate Comirnaty (Pfizer). Severely immunocompromised children who received 1 dose of Spikevax (Moderna) should receive a further 2 doses of Comirnaty (Pfizer) 8 weeks apart to complete the primary course. Severely immunocompromised children who received 2 doses of Spikevax (Moderna) should receive 1 further dose of Comirnaty (Pfizer) 8 weeks later to complete the primary course. 


Authors: Francesca Machingaifa (MVEC Education Nurse Coordinator) and Rachael McGuire (MVEC Education Nurse Coordinator)

Reviewed by: Rachael McGuire (MVEC Education Nurse Coordinator) and Katie Butler (MVEC Education Nurse)

Date: December 2023

Materials in this section are updated as new information and vaccines become available. The Melbourne Vaccine Education Centre (MVEC) staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family’s personal health. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult a healthcare professional.