5.3 Vaccination Te rongoā ārai mate
5.3 Vaccination | Te rongoā ārai mate
Vaccination is an important tool humans have used to fight pandemics for over two centuries. The smallpox vaccine was the first vaccine to have been developed against a contagious disease. In 1796, British physician Edward Jenner demonstrated that an infection with the relatively mild cowpox virus conferred immunity against the deadly smallpox virus.
5.3.1 The influenza vaccine | TTe kano ārai mate rewharewha
Early attempts at a vaccine during the 1918–1919 influenza pandemic were based on the belief that influenza infection was caused by bacteria. It was not until 1933 that the influenza virus was isolated and identified.
The first influenza vaccine was developed by Thomas Francis and Jonas Salk at the University of Michigan and tested on the United States military, before being licensed for wider use in 1945. Advances in science have meant that the time from the identification of a pathogen to the deployment of an effective vaccine has been drastically reduced (Figure 49).
Figure 49: Vaccination innovation, 1880–2020
Period from pathogen identification to United States licensing of a vaccine
Source: Our World In Data
Notes:
1. In 2021, the malaria vaccine RTS,S/AS01 was recommended by the World Health Organization for widespread use among children in sub-Saharan Africa and in other regions with moderate to high P. falciparum malaria transmission.
2. The only approved vaccine is bacilli Calmette=Guérin (BCG), developed in 1921 but its efficacy in adults is variable. Other tuberculosis vaccines are currently in development.
3. Partially effective vaccines CVD-TDV (sold under the brand name Dengvaxia) and TAK-003 (Qdenga), others in development.
4. Successful first human clinical trials of a vaccine against the virus in 2016. The World Health Organization issued statements of concern about the Zika virus' link to Guillain-Barré Syndrome (GBS) and microcephaly in 2016.
5. Several vaccine candidates are under investigation.
6. Not all cervical cancers are caused by the HPV virus, and the HPV vaccine can protect against other cancers caused by the HPV virus.
7. Several vaccine candidates have been trialled without success. Some potentially promising candidates are currently in phase I trials.
Influenza led to the death of millions of people in the 20th century (section 2.1). The pandemic of 1918–1919 was caused by the H1N1 strain; it led to the deaths of 50 million people. More recent outbreaks of H2N2 (Asian) and H3N2 (Hong Kong) flu in the 1950s and 1960s led to millions more deaths.
With the availability of a vaccine, influenza became much less deadly. In the decades after the Second World War, 30–60 per 100,000 New Zealanders died from influenza and pneumonia (Figure 50). As the vaccine became available, numbers began to fall. In 1997, free influenza vaccination was made available to those aged 65 years and over in New Zealand, and in 1999 free vaccination was extended to at-risk groups under 65 years. Although mortality from influenza had been dropping since the 1960s, the effect of free vaccination is noticeable, with mortality dropping from around 20 per 100,000 population during the early 1990s to single digits. The mortality gap between men and women has also narrowed.
Figure 50: Deaths from influenza and pneumonia in New Zealand, 1948–2022
Deaths per 100,000 people from influenza and pneumonia, by sex
Source: Health New Zealand I Te Whatu Ora, New Zealand Mortality Collection
5.3.2 The impact of COVID-19 restrictions on respiratory infections | Te pānga o ngā here KOWHEORI-19 ki te horapa o ngā matehā
Influenza, along with other diseases that can lead to severe acute respiratory infections (SARI), peaks in the winter months. The left panel (a) of Figure 51 shows the rate of hospitalisation due to all SARI for weeks 18 to 38 (April/May to September) of the five years prior to the COVID-19 pandemic, along with the incidence for 2019 and 2020. SARI incidence peaks in week 29 (mid-July) at 8 per 100,000 people. During 2020, when movements were restricted, SARI incidence dropped considerably, not rising above the seasonal threshold. The right panel (b) shows the equivalent rates just for influenza. The 2019 influenza season arrived earlier than normal. In 2020 the restrictions placed on movement to control COVID-19 meant that not one person in New Zealand was hospitalised because of influenza.
Figure 51: Hospitalisations for severe acute respiratory infections
Hospitalisations per 100,000 people by week of year for all SARI and influenza-associated SARI, 2015–2019 average, 2019 and 2020
Source: Q. Sue Huang and others, 'Impact of the COVID-19 nonpharmaceutical interventions on influenza and other respiratory viral infections in New Zealand'. Nature Communications, Volume 12, Issue 1 (2021), pp 1–7.
5.3.3 COVID-19 vaccination in New Zealand | Te rongoā ārai mate KOWHEORI-19 i Aotearoa
Once the COVID-19 vaccines began to be approved and manufactured, vaccination rates grew quickly across the world. Of our comparator countries, the United Kingdom, the United States, Sweden and Italy started their vaccination programmes before New Zealand, Australia and Japan (Figure 52). In the early months of New Zealand's vaccine rollout, higher-risk groups were prioritised, such as border workers, healthcare workers, and people with underlying health conditions. From August 2021, New Zealand's vaccination rate began to climb quickly, as eligibility widened to the general population. By mid-2022, vaccinations plateaued at rates between those of Sweden (74%) and China (92%). New Zealand achieved a total population vaccination rate of around 80%.
Figure 52 shows people vaccinated as a proportion of the total population, not of the population eligible for vaccination, and so it also reflects the vaccine eligibility rules of the countries shown. For example, vaccinations were not available to children aged 5-11 years until 17 January 2022 in New Zealand, whereas they were available in China and the United States from October 2021.
Figure 52: Cumulative first vaccine dose, 2021–2022
Number of people who received at least one vaccine dose, as a percentage of the total population
Source: Official data collated by Our World in Data, World Health Organization, Population based on various sources (2024) – with major processing by Our World in Data
Most of the widely-used COVID-19 vaccines were designed for a two-dose initial protocol. The average number of doses per person was 1.6 (160 per 100 people) in most of the comparator countries in Figure 53. The outliers were China with 1.8 and the United States with 1.3. Booster doses were required to maintain vaccination effectiveness. There was more variation in the number of booster doses, with Japan averaging 1.3 per person, but the United States only 0.2. New Zealand was similar to the remaining countries, with around 0.7 booster doses per person.
Figure 53: Total COVID-19 vaccine doses administered to July 2024
Total number of doses administered as part of the initial protocol (generally two doses), and booster doses, per 100 people, to 28 July 2024
Source: Official data collected by Our World in Data; World Health Organization
Note: Population relates to the whole population of a country, not just those for whom vaccines were made available.