Libresco: Weaker vaccines for better health

During Yale Summer Session, my “Epidemics in American Culture” class needed only two weeks to wipe out a good quarter of the earth’s population, and we were well on track to eliminate all but the most isolated tribes by the end of the month.

Our final class project was a crisis simulation of a bioterror smallpox attack, and we had completely failed to contain the spread of the disease. The simulation we were using was modeled on an official drill for government officials. The professionals managed to last a whole extra month before they killed off everyone.

The government scientists and my epidemics class made the same mistake during the simulation: We did not distribute enough vaccines. Smallpox containment depends on ring vaccinations, inoculating everyone who could be exposed so that, with no one left to infect, the virus fizzles out. Instead of deploying our vaccines quickly, we held them in reserve, panicked by the idea of running out.

Now, all my epidemiology classmates are getting to watch a full-scale pandemic, and, just as it happened in class, it’s all coming down to vaccination. And, once again, we’re not doing so well. This week, I went to get my DUH-provided flu shot. I was inoculated against a strain of H1N1 influenza, but not the swine flu strain that has been sweeping the campus. If I get a swine flu shot at all, it won’t be until at least mid-October, when the vaccines come off the assembly lines.

Scientists’ hands are tied by our antiquated system of producing vaccines. Vaccines are cultured in fertilized chicken eggs. The eggs are broken carefully, infected with flu and patched together. The chicken embryos, teeming with virus, continue to develop for months until scientists can harvest the amplified virus. Every year, 100 million eggs are used to develop vaccines for the United States alone.

The process of growing vaccine in chicken embryos takes too long to allow the United States to respond quickly to disease. Epidemiologists don’t have the luxury of time when transcontinental flights make every outbreak a pandemic.

The time lag imposed by egg-based vaccines means that scientists must begin guessing which three strains of flu against which they’ll need to vaccinate nearly a year ahead of flu season. Using reports from the CDC and samples from doctors all across the country, scientists try to predict which flu strains will be most common and then begin developing a vaccine cocktail accordingly.

We have better options. Scientists can produce virus proteins using cells grown in petri dishes. The proteins trigger enough of an immune response to protect against that strain of the virus. Because this method uses pre-existing human cell lines, it can produce usable vaccines much more rapidly than the egg method. But it’s not widely used in the United States today because it would require a substantial initial investment in new infrastructure and because this new method does not have a lengthy history of clinical trials as the egg-based vaccine.

Perhaps the real solution is simply to lower our expectations. The current system is designed to produce maximally efficient vaccinations, when we might be better served by producing less effective vaccinations that can be rolled out more rapidly. Today’s flu shots are 70 to 90 percent effective, but it is possible to significantly reduce the prevalence of flu, even at lower efficacy levels.

Vaccines provide protection against flu both by conferring immunity on those inoculated and by building up herd immunity. No vaccine is completely effective, but, when vaccination is widespread, it becomes difficult for a virus to spread through a population. The goal should be to build up herd immunity as quickly as possible to limit the spread of pandemic strains.

Up until now we have been lucky. The swine flu strain, although highly contagious, has been no more deadly than ordinary strains of the flu. But as a disease spreads more widely, it becomes more likely to mix with other strains and to pick up new traits that make it harder to treat. Containing the spread of swine flu can help us contain its lethality.

In an age of global disease, our vaccine policies can’t be conservative. We must fight infectious diseases aggressively, even if that requires us to put aside old standards of testing and efficacy. Our outmoded system of vaccination is inadequate; we must prepare ourselves for rapid responses to outbreaks if we hope to make it through the next pandemic.

Leah Anthony Libresco is a junior in Jonathan Edwards College.


  • Just a thought….

    Might it be more likely that the virus would mutate as it spreads through the population given the less effective vaccine? Vaccination “take” rates are less than perfect, and with a less than perfect vaccine that outcome could be amplified. Obviously, controlled study is necessary to answer this question, but it shows the need to take the time to fully research interventions so as to avoid creating even bigger problems.

  • Yale Engineer

    To be frank, while cell-based and cell-free allow for much more rapid development and higher throughput, the reality is that they are much more expensive to make. However, they are and should be the method of the future.

    I like what you have to say about developing herd immunity. In fact that might be one of the best strategies to reduce the damage and spread of malaria.

    However, the high efficacy rates are suppose to help the individuals. The problem with low efficacy vaccinations is that the value to the individual becomes lost. The net result is a large rise in anti-vaccinations groups and a decreased compliance. There are also problems as By Just a thought mentioned, that vaccines could drive evolution. A good example is the dengue fever vaccine which may actually kill people due to amplification rather than dampen the effect. Another relevant example is the most recent HIV vaccine from Thailand.


    So what you’re saying is that you took this class one time on something tangentially related to current events?

  • Leah Libresco

    Thanks for your comments. To respond:

    @Just a thought
    It’s certainly possible. However, one of the greatest risks of mutations is simple prevalence. As a virus is exposed to more environments and other similar viruses, it is more likely to develop harmful mutations. Hopefully, containing the spread of a disease might reduce the number of chances for mutation. But this is speculation on my part.

    @Yale Engineer
    You make a strong point. However, since we cannot achieve strong global coverage with vaccination, perhaps we are best off begininng by making our our own country as herd immune as possible, so that the spread becomes more logistically manageable.

    I know, right?