Why routine immunisation is vital for pandemic preparedness
Trying to control a pandemic can feel like being in a warzone, yet even as we fight COVID-19 we still need to keep one eye on the future and potential emerging pandemics. Dr Velislava Petrova, senior manager in vaccine policy and investment at Gavi, explains why.
- 3 May 2021
- 8 min read
- by Priya Joi
Q. Many countries are still battling COVID-19, yet the world needs to be prepared for the next pandemic – why is it so important for us to invest in preparedness even as we are responding to a pandemic?
The current pandemic really highlighted underlying challenges in health systems and the equitable delivery of health services that need to be addressed if we are to minimise the negative health and economic consequences of the next pandemic. COVID-19 showed us that there's a very limited ability to act reactively and to stop the spread of a pandemic once it has started. That's why we need to focus on prevention, which includes the early detection and control of outbreaks and the building of resilient health systems to address areas of vulnerability that can trigger future outbreaks.
We can use the momentum of this pandemic to build better systems for pathogen surveillance, diagnostics, case-tracking and reporting, health record management and reliable procurement and supply. There is a lot of infrastructure and capacity building that needs to be done.
The financial investment and health care costs for a response are a lot higher than if we invest in prevention. That's why it's extremely important to think about the future, even though we are in the middle of a pandemic.
A good example of how proactive action can make a difference was with Ebola. Gavi set up an Advanced Purchase Commitment mechanism for investment in Ebola vaccines, which assured manufacturers their product would be bought. This created an incentive to speed up the development of an Ebola vaccine that can be stockpiled and made available freely in outbreak situations. Through its commitment to contribute to a global emergency stockpile of 500,000 Ebola vaccine doses, Gavi and its Alliance Partners helped manage the most recent Ebola outbreak in DRC and neighbouring countries. This is only one of the many mechanisms for prevention that can make a difference next time we are in a situation of a global pandemic.
Q. What can cause an outbreak to escalate into an epidemic or pandemic?
Localised outbreaks happen all the time, but they don’t necessarily result in a pandemic. It’s the specific interplay between different pathogen characteristics and population dynamics that can lead to escalation of an outbreak. Important aspects of pathogen biology are route of transmission, ability to sustain human-to-human spread, pathogenicity, presence of an animal reservoir, etc. If we have a virus that has jumped from an animal reservoir, gained the ability to be highly transmissible amongst humans who don’t have previous immunity and causes an infection with moderate mortality to allow it to continue to spread without killing its hosts, outbreaks can quickly become difficult to control. Similar scenarios have been the trigger of most major epidemics.
Yet, the pathogen characteristics are only part of the picture. The context in which an outbreak occurs and how quickly it is detected also plays an important role. If outbreaks occur in highly populated areas, individual infections can turn into super-spreader events that affect large numbers of people. In places where there is close human-animal interaction, such as farms or food markets, pathogens can jump from animals into humans, who may never have encountered this pathogen before. When such infections are not detected in time they start spreading from a small community to the rest of the country. And in a world so connected through transport and trade, this can quickly pose a threat to the rest of the world and make an individual outbreak turn into a global pandemic.
Finally, pathogen biology and population dynamics cannot be seen as two independent factors, but rather as a continuous host-pathogen interaction which can be affected by broader economic, environmental and anthropological processes. Changes in the ways of living of humans and animals on a global level can affect the epidemic potential of individual outbreaks. This can include urbanisation, which leads to people living in close proximity, climate change, which leads to global spread of animal vectors that carry human disease, or people needing to find new ways of making a living in new geographies and thus increasing the spread of otherwise endemic pathogens.
Q. Many diseases with pandemic potential originate from animals, so presumably as well as building our laboratory capacity and surveillance capacity, we need to focus on hotspots of potential spillover?
Yes, that's why often in terms of epidemic diseases, we talk about a One Health approach, as a way to think about disease prevention and control across both animals and humans as a united effort. The ability to control a disease in animals can often be critical to preventing its spread in people. One example is Rift Valley Fever that affects cattle and other livestock but can spread from animals to people and cause outbreaks.
Q. Much of the focus is on using COVID-19 vaccines to slow the current pandemic, but actually routine immunisation – which was paused in many countries last year – can be so important for pandemic preparedness. Can you explain why?
It's important to remember that other pathogens have not stopped spreading now that we have COVID-19. If we allow prolonged drops in herd immunity because of delays in routine immunisation we would compromise years of efforts to control deadly diseases and put many vulnerable communities at risk. Pandemics prompt us to think about the connectedness and interdependence between countries, and to understand that we need global efforts with removal of silos in health systems.
This means rather than thinking about diseases individually, we need to really understand where the vulnerabilities in healthcare systems lie. And that's why expanding and strengthening the systems for routine immunisation and achieving equity in access to vaccines is really a stepping stone towards achieving better preparedness. When we reach people with routine immunisation, it is a way of linking them to the primary health care system. It can mean they have access to other healthcare services, and it can ensure that they are on the grid.
Once the infrastructure for delivering routine immunisation is in place, and people in the community have a connection with vaccination as an important part of public health, emergency vaccination such as for COVID-19 is much easier to deliver.
And that's why as part of Gavi 5.0, our new 2021-25 strategy, we are really focused on reaching zero-dose children, those children who never get a single routine vaccination and are in the most marginalised communities, living in poor housing, often amid conflict, and with limited access to education and primary health care services. Reaching these children is so important because they live in an environment that has all the conditions for another outbreak.
Q. Do you think that the world is becoming more aware of the importance of routine immunisation?
Immunisation has never been the focus of public attention more than it is now. But we've certainly understood that vaccination is one of the best tools in the plethora of public health interventions we have. We have limited options to control infections without them. Unless we achieve high immunisation coverage for deadly diseases such as measles and diphtheria, we cannot really be protected. Even if the disease is not endemic in our own country, the fact that it exists somewhere else in the world means we are still at risk. I think now we all understand what a privilege it is to have vaccines for certain diseases, and how it's crucial to make sure that everyone, everywhere has access to those vaccines.
Q. The World Health Organization (WHO) and the Coalition for Epidemic Preparedness Innovations (CEPI) have identified diseases that could become major epidemics or pandemics. So how do we prepare for a range of potential threats, and how do we predict which disease is likely to be the next problem?
Epidemic and pandemic preparedness shouldn't really be seen as looking into a crystal ball and trying to guess what is coming next. We need to focus on continuous monitoring of the way diseases evolve, understanding areas of vulnerability in populations, creating mechanisms to fast-track vaccine development, and then building strategies for the sustainable deployment of immunisation programmes in countries.
That's why in 2019, we initiated work at Gavi on what we call ‘living assessments’ for those pathogens with high outbreak potential identified by WHO, CEPI and other partners. With this work we aim to gather relevant information on where disease spreads and what the magnitude of a potential outbreak could be, to identify whether there are any vaccines in the pipeline and what is their impact and feasibility of use in the event of a future outbreak. This creates a situation report that is continuously updated and enables more agile decision-making in the future. This way Gavi can use its comparative advantage as an organisation to contribute to broader epidemic preparedness efforts and benefit the global community.