Immunisation (vaccination) is one of the best ways to limit the spread of disease. Prior to 1960 only a few vaccines were available in New Zealand. People were often vaccinated in response to a disease outbreak or as part of specific immunisation programmes. Doctors were authorised to decide the age at which a child should be immunised.
In 1960, the Health Department introduced a national immunisation schedule which recommended vaccination against certain diseases at specific ages. Initially only the combined diphtheria-tetanus-pertussis (DTP) vaccine was offered. The schedule later expanded to include many other vaccines, which are given free of charge starting at six weeks of age.
Since the introduction of the schedule, immunisation has successfully controlled diseases such as hib disease (haemophilus influenzae type B, which can cause meningitis and epiglottitis), which has been virtually eradicated. Other vaccines on the schedule, such as the HPV vaccine, have the potential to be equally effective.
How immunisation works
People are immunised against infectious diseases with vaccines, which contain either fragments of a disease germ or weakened germs. These prompt the body to produce cells and antibodies that protect the person from the disease. Vaccinations have been widely used since the 19th century. To prevent some diseases, such as measles, from circulating in the community, at least 95% of the population needs to be vaccinated. Te Whatu Ora Health New Zealand’s national immunisation target is 95% of two-year-olds fully immunised – in 2023, 83.1% were fully immunised.
In 2008, the Ministry of Health introduced a programme that made vaccination against the highly infectious HPV (human papillomavirus) available to young women born in 1990 and 1991. From 2017 the vaccine was free for every female aged 9 to 26. It was delivered primarily through schools. The aim was to protect young people from the sexually transmitted HPV virus before they became sexually active. HPV has been linked to cancers of the cervix, mouth and tongue, and other invasive cancers. Vaccination is extremely effective, and full implementation of the programme would save many lives. New Zealand has yet to reach its target of 75% of the population fully immunised.
Legislation and regulation
In epidemic or pandemic situations, the Health Act 1956 and regulations issued under it give local medical officers of health special powers. They may quarantine or disinfect people, vehicles or animals, restrict the movement of people into or out of an area, close premises such as schools, and commandeer resources needed to fight the disease. In very serious situations, a state of emergency can be declared, giving the authorities additional powers to control behaviour.
Because the public health response to the outbreak of COVID-19 in New Zealand was so complex, special legislation was required. The COVID-19 Public Health Response Act 2020 gave the Minister of Health numerous powers, including the ability to order people to self-isolate, to wear masks and to restrict their movements, even if they were not infected with the disease. In addition, a national state of emergency was declared in March 2020, the first time one had been imposed for a pandemic.
Updating regulatory standards can also help to control the spread of disease. A campylobacteriosis (a gastrointestinal disease mainly caused by eating chicken that has not been properly cooked) epidemic peaked in 2006 and then abated, probably due to new regulatory standards in the poultry industry.
Because of the ongoing risk of epidemics, health practitioners and medical laboratories are legally required to notify the local medical officer of health if they suspect or confirm a case of certain diseases, including measles, tuberculosis and many respiratory diseases. Since 2016 it has been possible for doctors to report a few of these diseases, including AIDS and HIV, without providing the name of the patient.
The Institute of Environmental Science and Research, a Crown research institute, monitors infectious diseases and provides information to the Ministry of Health on disease rates and distribution, identifies outbreaks, monitors interventions and predicts emerging disease hazards.
The Ministry of Health monitors infectious diseases and oversees programmes delivered by Te Whatu Ora Health New Zealand to contain them and minimise their effects. In an international context, the ministry works closely with the World Health Organization (WHO), providing the United Nations agency with New Zealand health statistics and other information.
New Zealand committed itself to playing a role in international work to combat the spread of diseases by signing up to the International Health Regulations (IHR) 2005. The IHR are an agreement developed by WHO member countries to combat the spread of disease and other public health hazards. Member countries have a responsibility to develop measures to prevent, prepare for and respond to public health events, while avoiding disruption to international travel and trade. They are also required to inform the WHO of any public health event that risks spreading across borders. In 2022, member countries agreed to amend the IHR to incorporate lessons learned from the COVID-19 pandemic. Ashley Bloomfield, New Zealand’s former director-general of health, was selected as a co-chair of the working group to amend the regulations.
During the COVID-19 pandemic, New Zealand purchased and donated millions of doses of vaccine to countries in the Pacific and elsewhere that could not afford to buy them.
Barriers to disease control
Though epidemics have become less frequent, studies have found that hospital admission and discharge rates for infectious diseases have been increasing since the 1980s, if not earlier. This counters the prevailing understanding that these diseases have become less of a burden. As international air travel became increasingly affordable, New Zealand was no longer isolated from the spread of diseases such as HIV/AIDS, SARS (seasonal acute respiratory syndrome), influenza and COVID-19.
Falling global and national childhood vaccination rates in recent years mean New Zealand is at risk of outbreaks of serious diseases. A combination of misinformation and an emphasis on COVID-19 vaccination and protective health measures has seen less time and effort put into preventing the spread of other serious illnesses such as measles. In addition, poor recordkeeping about childhood immunisation, especially in the 1990s and early 2000s, has made it difficult for children born in those years to find out if they are immunised against certain diseases.
Climate change may increase the likelihood of some tropical diseases reaching New Zealand. Diseases such as dengue fever, Zika virus and Ross River virus are not currently present in New Zealand’s mosquito population. Rising temperatures and increased rainfall may allow disease-carrying species of mosquito to establish populations here, leading to local outbreaks.