As vaccine hesitancy threatens hard-won gains, Australia and other wealthy countries must do more to support low- and middle-income countries to boost childhood immunisation, Burnet Institute Director and CEO Professor Brendan Crabb AC, and Associate Principal Research Fellow Professor Mike Toole AM write for Croakey News.
In this article marking World Immunization Week (April 24-30) we look at the achievements of immunisation since the first vaccine was invented in the 19th century against smallpox.
This vaccine eventually led to the global eradication of smallpox in 1980 - the first and only human infectious disease to have been eradicated.
Here, we focus on the global impact of immunisation on the health of children. But we also provide examples where child vaccination prevents illness and deaths in adults.
We look at setbacks to immunisation, both in terms of access to vaccines and willingness of parents to vaccinate their children, since the onset of the COVID-19 pandemic.
For obvious reasons, over the past three years almost any mention of immunisation has involved vaccines against SARS-CoV-2, the virus that causes COVID-19.
However, COVID-19 vaccination has been marked by widespread misinformation, which has even been politicised, especially in the United States but also by some politicians in Australia.
This misinformation likely at least in part explains why only 51 percent of Australian primary school children have received two doses of COVID vaccine.
Global benefits
Immunisation has changed the course of human history, a public health intervention rivalling clean water and sanitation for its profound impact on human survival and wellbeing. Because of improved vaccine-driven child survival, life expectancy has increased markedly over many decades.
It is an extremely cost-effective public health measure, and as a result is available to most children in every country in the world. For example, a study of 94 low and middle income countries (LMIC) found that one US dollar invested in immunisation against ten pathogens returned 52 US dollars between 2011 and 2020.
Similarly, work published in 2021 found that 37 million deaths were prevented by vaccination against ten pathogens in 98 LMICs between 2000 and 2019. Modelling predicted that this number would increase to 69 million by 2030. The vast majority of prevented deaths were in children less than five years of age.
Vaccine hesitancy has increased
The World Health Organization (WHO) has documented decreases in child vaccination rates globally since the commencement of the pandemic.
The WHO estimates that in 2021, 25 million infants under the age of one year did not receive basic vaccines through routine immunisation programs. This was a staggering six million fewer children immunised than in 2019, the most unvaccinated since 2009.
A UNICEF study published in State of the World’s Children on 20 April found that parents’ confidence in childhood vaccines had fallen in 52 out of 55 countries since 2019. Australians’ confidence in childhood vaccines has dropped 7.5 percent – from 93.8 percent before the pandemic to 86.3 percent in 2021-22.
One of the largest declines was in Papua New Guinea (PNG) where confidence in vaccines fell from 90 percent pre-pandemic to just 46 percent in 2021-22.
While there are now vaccines against 25 pathogens, we highlight both achievements and challenges associated with five vaccines.
MeaslesMeasles is often a mild illness; however, some children – especially in LMICs – have severe disease that may include diarrhoea, pneumonia, middle ear infections and malnutrition, and may lead to death. It is also associated with long-term sequelae including sub-acute sclerosing panencephalitis and immune dysfunction.
Between 2000 and 2018, measles vaccination prevented an estimated 23.2 million deaths. Global measles deaths have decreased by 73 percent from an estimated 536,000 in 2000 to 142,000 in 2018.
Polio
Wild poliovirus cases have decreased by over 99 percent since 1988, from an estimated 350,000 annual cases to 22 reported cases in 2022 and one case so far in 2023.
The success of the global polio vaccination campaign is in large part due to an effective coalition of Rotary International, WHO, UNICEF, the GAVI Alliance, US CDC and the Gates Foundation.
A recent challenge has been outbreaks of circulating vaccine derived polio virus (cVDPV), which occurs when the vaccine virus mutates and spreads in populations with low vaccine immunity. In 2022, outbreaks of cVDPV occurred in Jerusalem, New York State and was detected in wastewater in London, where vaccination rates were very low.
Hepatitis BThe hepatitis B virus (HBV) can be transmitted from mothers to infants during pregnancy and childbirth. In some infected people, the virus persists chronically (HBsAg) and leads to liver cirrhosis, cancer and death in adulthood.
The prevalence of HBsAg in Indigenous Australians is four times higher than in the non-indigenous population.
However, after an infant and adolescent HBV vaccination program was introduced in 2000, numerous studies showed that the prevalence dropped on average from around 11 percent to 3.5 percent by 2018. This is a significant achievement.
Papilloma virus
Cervical cancer is the fourth most common cancer in women causing an estimated 342,000 deaths in 2020. Human papilloma virus (HPV) causes around 95 percent of cervical cancer cases. A very effective vaccine is recommended for children aged 12-13 years and reduces the incidence of cervical cancer by almost 90 percent.
However, there are great disparities between countries in access to the HPV vaccine.
While more than 85 percent of high-income countries had introduced HPV in 2021, less than 25 percent of low-income and less than 30 percent of lower-middle-income countries had done so. Around 90 percent of cervical cancer deaths occur in these countries.
Influenza
Influenza viruses mutate often and every year, a new vaccine is developed based on the most recent virus circulating in communities.
The recent coverage of influenza vaccination in Australia has dropped in the vulnerable age group of six months to five years.
In 2022, despite the vaccination being free for these children, only 32.4 percent of children in this age group received their flu shot, compared to almost 70 percent of those aged 65 and over.
Remaining challenges
It is imperative that global child vaccination rates return at least to pre-pandemic levels.
This can be achieved through a combination of government commitment, community engagement and support for strengthening health systems in LMICs.
Australia could play such a role in neighbouring countries such as PNG where, for example, only 38 percent of children in 2022 had received one dose of measles vaccine.
Wealthy nations should also help expand access to HPV vaccination (through investment in the GAVI Alliance) in LMICs and continue to support the last stages of polio eradication.
Further investment in research and development is needed to develop effective and affordable vaccines against HIV, malaria, tuberculosis, hepatitis C and neglected tropical diseases.
Australian governments need to address the barriers to child COVID and flu vaccination. Regarding the low two-dose coverage of COVID vaccine in 5 to 11 year olds, a forum of child vaccination experts and researchers convened in March 2022.
They identified key challenges and barriers to Covid vaccination. These included:
- A 19 percentage point gap in coverage nationally between Aboriginal and Torres Strait Islander children and non-Aboriginal children.
- A 28 percentage point gap in coverage between people living in the highest (64 percent) and lowest (36 percent) socioeconomic areas.
- Low perceived need for a vaccine due to low perceived risk of severe disease; perception that the vaccines are not effective; and safety concerns.
- Clear, consistent messaging needs to be appropriate for the demographics of the target population.
Although Australia has an excellent record of routine vaccination in childhood, the contradictory low coverage by COVID and flu vaccines needs to be addressed.
While COVID and flu are usually mild in young children, sometimes they are not, as is the case for measles and polio. As the UNICEF study showed, confidence in all vaccines has dropped in Australia.
When overall case numbers are high, COVID-19 is a significant cause of severe illness and death in children; in the US, COVID-19 was the leading cause of death from infectious diseases in children in the 12 months to August 2022.
There is also the chronic impact of COVID in children, and evidence is emerging that vaccination reduces the likelihood of long COVID.
To address this vaccine hesitancy, targeted and informed community engagement is essential.
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