Why does it take a year to make a vaccine?

I pretty much stopped with biology classes after high school so really asking here.

My understanding is a vaccine is either a dead or inactivated pathogen or a severely weakened one. They inject you with it, your body sees it and learns to make antigens but since the vaccine was dead/weak bad stuff you don’t get sick.

So, is it a manufacturing problem or is there some reason they cannot get their hands on dead/weakend COVID-19?

To be clear, I have no doubt it takes a year or more to make a vaccine. This is not a conspiracy thing I am after. I am just trying to understand.

It doesn’t take a year to make one. It takes a 12-18 months to test one enough to make sure that you don’t kill more people than you save with your vaccine. To make it safe and effective you need to test it properly; and that takes time.

Because they want to make sure it works properly and there aren’t any serious side-effects. Remember thalidomide?

Thalidomide is a drug, not a vaccine.

Vaccines, I thought, were pretty straight forward. Put some dead pathogen in a solution and have at it. The solution is the same (I think) for all of them so that is well tested.

The only thing that changes from one to the next is the pathogen.

As long as the pathogen is dead/inactive I’m missing the problem.

Again, I am sure they have very good reasons for this and it may well be testing and I am all for having them do this safely.

It’s a little more complicated than that. For safety reasons, they don’t want to use actual dead, or inactive, pathogens. They use a biological preparation that is very similar to those, or sometimes composed of broken-down bits. The reason for this is to avoid ever infecting the patient, even by chance.

The more complicated answer is that these things take time. You’ve reduced it to one “step,” but there are dozen or hundreds of actions that have to take place to produce that step, each of which need to be documented, verified, and confirmed as safe. Then there is the actual problem of stepping up production and getting the vaccines into the market. A year is actually pretty short for all that - most medical products simply don’t get created and released in that kind of time frame. Fortunately, the expertise in Flu vaccines undoubtedly helps.

How do they get a yearly flu vaccine out? I know they have to do some guess work but I thought they were looking 6-9 months ahead and not 18-24 months ahead. At that point it seems near impossible to predict which flus to vaccinate against. I know as it is now it is still hit and miss but I thought is was better than just a dice roll.

It’s all the same process, but they know exactly has to be done, and since it’s an annualized task anyway so it’s planned and scheduled in advance. And as you point out, it’s still speculative and they don’t always get it right. The reason for the inaccuracy is exactly because the preparation time is too long to have the exact virus mix we’ll face once the actual flu season starts.

The yearly flu vaccine is a mix of already tested flu vaccines that are projected to be most effective in the upcoming year.

This is certainly true, and given public suspicion regarding vaccination it is really important not to release a vaccine that does any harm; the Cutter Incident (in which a mispreparation fo the Salk-process vaccine exposed 200,000 people to active poliovirus) and the later contamination of polio vaccine with SV-40 (which potentially exposed many people to increased incidence of various cancers) highlight the dangers of insufficient testing and quality control in vaccine development and production.

The o.p. has a very simplified notion of what creating a vaccine for a novel pathogen is actually like. Although attenuated vaccines (using ‘live’ or more properly active but disabled) viruses are sometimes used the preference is to use an inactivated virus or better yet fragments of viral proteins which stimulate an effective immune response without the chance of actually causing an infection or cross-mutation with another strain of the virus.

Even in the era when we can sequence the viral genome and produce a partial analogue of the genome with CRISPR-Cas9 technology, immunologists still have to find a way to produce the vaccine, assure that it is stable in formulation, easy and reliable to distribute, and does not have unintended consequences like stimulating an unexpected immune response. And of course, you need to evaluate the effectiveness of a vaccine because not everyone will respond the same, hence the need for three phase safety and efficacy testing before wide distribution so that people don’t believe that they have an immunity that they don’t.

The seasonal influenza vaccines are a special case, in part because influenza is somewhat unique among viruses for its ability to engage in recombination where two strains in the same person can swap genome material and suddenly become more virulent; hence the need to guess at what strains are going to be the most prevalent and tailoring vaccines to them. Although you may not know it, there are actually multiple different vaccine formulations produced each year which are given dependent upon region, age of recipient, and any known reactions or allergic factors.

The question shouldn’t be “Why does it take a year to make a vaccine?” but rather, “Isn’t it amazing that immunologists can produce what is essentially an entirely new immunization treatment in only a year or two?” Most effective pharmaceutical developments are the result of many years—sometimes decades—of research and development, testing, and many blind alleys before finding something that works, and in the world of pharma vaccines are almost uniquely effective in that when they are well developed they provide nearly universal benefit with almost negligible side effects. You can’t even say that about OTC drugs like aspirin or NSAIDS.


Well, biologists argue about whether a virus (like Covid-19) is ever ‘alive’ at all. So it’s pretty hard to tell if it’s really ‘dead’, or just resting and waiting to reactivate once it’s in a suitable host (like a human body). They’d like to do a fair amount of testing so as to have answers to that before injecting it into too many thousands of people.

Are you suggesting it may be pinin’ for the fjords?

As far as weakened virus vaccines, the polio vaccine used in much of the world is of that type. And it does happen that it’ll mutate and become virulent again. I don’t know what the current status is, but a couple years ago, there were more cases of paralysis caused by that than by wild polio viruses: Mutant Strains Of Polio Vaccine Now Cause More Paralysis Than Wild Polio. That mostly shows how effective the eradication effort has been, but it’s unfortunate they have to use that type of vaccine, rather than the other one that doesn’t have weakened viruses in it.

The point remains valid, though. The thalidomide disaster was the landmark event that led to the Helsinki Declaration, which is really the beginning of modern pharmaceutical ethics.

It’s also worth pointing out that you can tolerate even less risk with a vaccine than with other medicines, because of who you give it to. Compare to something like chemotherapy for cancer: It has terrible side effects, and can in fact kill the patient, if you’re unlucky. But the people you give chemotherapy to are people who would almost certainly die if they didn’t get it. When your baseline is a patient who’s almost certainly going to die, something that only might kill them is worth it. But a vaccine, you give to healthy people. The hope is that you’ll be giving it to everyone, or very close to it. So even a very small risk of serious side effects isn’t acceptable, because those side effects would always be worse than what the patient would have without it.

Incidentally, there are already vaccines for this coronavirus. Several of them, in fact. Making those vaccines didn’t take long at all. Everything we’re waiting for now is the testing. Well, and the large-scale production, but that step can be sped up considerably with appropriate funding.

As I understand, some (or all?) of the vaccines being tested are mRNA vaccines. These are very different from conventional vaccines - essentially, these are artificial viruses cause your body to produce proteins that are on the actual coronavirus. They are much faster to produce than conventional vaccines, which is why they already have vaccines available for testing.

There’s also something called antibody-dependent enhancement (ADE), which can occur with some viruses. Short version: in those cases, if you have no antibodies you can get the disease, if you have a full antibody response you won’t get the disease, and if you are “in between” with a partial antibody load you are not only susceptible to the disease but if you catch it, you will have a more severe and dangerous case than if you had no antibodies in the first place. ADE has led to the recall of some vaccines in the past, notably of a dengue fever vaccine in the Philippines a few years ago where being vaccinated left kids more susceptible to life-threatening complications if they encountered the disease “in the wild.” Can ADE happen with coronaviruses like one causing COVID-19, and if so, how do you make sure the vaccine doesn’t lead to this?

There are literally dozens of coronavirus vaccine candidates. You don’t want to spend billions of dollars rolling out a particular vaccine, only to find out it’s considerably less effective than another one. Safety is one important consideration; efficacy is another.

Antivaccine advocates are drooling at the thought of a flawed vaccine being rushed to market so they can use the example to damn all vaccines. We don’t want to give them ammunition for their “cause”.

The problem with mRNA vaccines is finding a way to deliver them to the patient that does not provoke a severe immune response. This far there have been no mRNA vaccines actually approved to market (that I’m aware of) although there have been some promising trials. Here is the National Institutes of Health webpage on the clinical trial of an mRNA vaccine developed in partnership between NIAID and Moderna.

Not only could it happen; it was actually a problem with vaccines being developed for the SARS-CoV(-1) and MERS-CoV viruses, which is yet another argument for not just racing past the normal phased safety and efficacy trials. This pandemic is bad enough without making mortality an order of magnitude worse through lack of oversight and due diligence.


Actually Bill Gates is spending a few billion on setting up production for seven different vaccines before knowing which one will be most effective, on the theory that the money wasted on the six they end up not producing is worth it to have the seventh in mass production the moment it’s known to be most effective.

This is of course the sort of thing that shouldn’t require a philanthropist to fund.

My question is, how bad would a disease have to be before the government said fuck it, here’s an inadequately tested vaccine, the side effects couldn’t possibly be worse than the disease, start handing it out.

Something as infectious and deadly as the black death, passed on by breathing on someone and surface contact?

  1. On average about 7 people a year get the plague (Yersinia pestis). If it was reasonably infectious the number would be much higher. Modern sanitation practices, rat control, etc. keep it down.

  2. We already have a cure for it, they’re called antibiotics.

Not a comparable disease.