Balancing Vaccination Strategies in Mpox Outbreaks

Right now, around the world, there are two different types of Mpox outbreaks happening at the same time. The one that’s particularly concerning is in central Africa, where the case rates and the number of people getting sick is on the rise. The current death rate is about 2%, which isn't great, and it's even higher among kids. Fortunately, there are Vaccines that have shown to be effective against mpox. Studies have indicated that these vaccines can help prevent the disease and make it less severe for those who do get it. While it’s a relief to know that vaccines exist, the problem is that there aren’t enough Doses available in the places that need them the most.

#The Vaccine Situation

The African CDC estimates that around 10 million doses are needed to tackle the outbreak. Japan has promised to donate 3 million doses, but unfortunately, these haven't yet made their way to central Africa where they’re urgently needed. Recently, about 200,000 doses of a specific vaccine arrived in the Democratic Republic of Congo (DRC). This vaccine requires two shots, given four weeks apart, to work best.

So, with limited vaccines, the big question becomes: how do we use what we have in the best way to prevent the most cases of illness, especially serious ones?

#One Dose or Two?

Studies show that one dose of the vaccine provides a certain level of effectiveness, and two doses provide even more. The World Health Organization (WHO) claims one dose gives around 76% effectiveness, while two doses provide about 82%. But there’s a catch. If many people only get one dose, even if it’s not as effective as two doses, we'd still prevent more cases overall. However, we also need to think about how long that protection lasts after a vaccine is given.

In our analysis, we focused on what would happen over two years. Even after a single dose, the protection can start to fade. If we want to maximize the number of people protected, it seems better to give out one dose to many people rather than giving two doses to fewer individuals.

#The Delayed Second Dose Dilemma

Now, let’s throw another twist into our story. What happens if supplies are delayed and the second dose isn’t available until a lot later? Studies have shown that waiting longer before giving that second dose can actually lead to stronger immune responses. So, in this case, should we stick with giving one dose to as many people as possible, even if that means delaying the second dose?

Throughout this analysis, we agreed that, generally, giving one dose to many people would still be the best route to take initially. Even when considering that a delayed second dose might enhance immunity, it's still more beneficial to give first doses to a wider group.

#Risky Business

We also have to think about not just the number of cases but who is getting sick. Not everyone is at equal risk of getting mpox. For example, children, especially those under five, are more susceptible and have a higher chance of severe illness. So, we need to question whether it’s better to focus on giving that second dose to people who are at higher risk or continue giving first doses to those at lower risk.

When the High-risk Group has already gotten their single dose, we have to decide whether to give them a second dose or start vaccinating the lower-risk group. If we are giving the second dose to the high-risk group, that could be an optimal choice if their risk of infection is significantly higher.

#The Numbers Game

When looking at the data, we found that unless a high-risk group is over nine times more likely to be infected than a lower-risk group, we should prioritize giving first doses to the broader group. And if we are trying to avoid severe cases, we'd ideally want to keep giving first doses to more individuals unless the high-risk group has more than a thirty-three times greater risk of severe illness.

However, if those second doses only become available a bit later, then we lower the threshold for when we might want to give those doses to the higher-risk group. If the high-risk group is only three to fifteen times more likely to get severe illness, it might make sense to target them for the second dose.

#Preventing Serious Illness

We also can’t ignore how severe mpox can be, especially for certain demographics like children. Because of this, it’s crucial to think about how the vaccinations should be structured to reduce severe outcomes.

Based on the limited available data, it appears that the vaccine is pretty effective in preventing serious cases. If our goal is to minimize severe cases, it still seems best to continue giving one dose to many people unless the high-risk group’s risk of severe illness significantly surpasses that of the lower-risk group.

#Conclusion: It’s All About Making Choices

Ultimately, the constant juggling act remains. The need for vaccines is huge, but supply is low. While it might be tempting to cover as many people as possible initially, the specific risks of various age groups and health statuses mean that careful planning and strategic choices regarding who gets vaccinated first are essential.

In the face of a public health crisis, we’re in a position where every vaccination decision counts. So, let’s make sure we’re doing what’s best for the greater good while keeping an eye on those most at risk. Because, after all, a stitch in time saves nine, or in this case, a dose now could save a life later.