What Are the Different Types of Vaccines?

What are the different types of vaccines?

Paul Offit, MD: Hi, my name is Paul Offit from the Vaccine Education Center. One of the basic questions we get asked about vaccines is: How do you make them? So, I'm going to divide this up into two categories. One is viral vaccines, the second is bacterial vaccines.

So, for the viral vaccines, there are a number of different strategies. You can take the virus, grow it up, purify it, and then disable it (kill it, inactivate it) with a chemical. So that's the way we make the inactivated polio vaccine, the hepatitis A vaccine, and the rabies vaccine.

Or you can take a virus and then weaken it, weaken it in the laboratory so that it can still reproduce itself in people, but much, much less so than the normal, or native, or natural virus. So, you can induce an immune response without having to suffer the disease. That's the way we make the measles vaccine, the mumps vaccine, the German measles (or rubella vaccine), the chickenpox vaccine, and one of the rotavirus vaccines. Or you can just take one protein of the virus, one part of the virus, which is the way we make the hepatitis B vaccine and the human papillomavirus vaccine, and one of the influenza vaccines.

More recently, with the COVID-19 outbreak, there are two new strategies that have been employed. One of which, here in January 2021, is already being used, the so-called messenger RNA vaccine. So here what you do is instead of inoculating someone with just a protein from the virus, in this case the SARS-CoV-2 spike protein, what you do is you inoculate them with the gene that codes for that spike protein. So, your body then makes the spike protein, and then your body makes antibodies to the spike protein. And that's the way these two messenger RNA vaccines are being made.

Another strategy that's being used and it hasn't been introduced into the United States yet, but likely will be, is to take a so-called replication-defective human adenovirus, or replication-defective simian adenovirus. So, by replication defective I mean, the virus can't reproduce itself, and therefore can't possibly cause disease. But what it does is it serves as a Trojan horse to bring that gene that codes for the spike protein into the cell. So in many ways, it's just like the messenger RNA. In the case of messenger RNA, it's just sort of a naked piece of RNA; here, it's you bring the gene in via the virus and then, ultimately, mRNA is made and the protein is made. So that's two other strategies. So-called replication-defective human adenovirus, which is Johnson & Johnson strategy, or replication-defective simian adenovirus, which is the UK AstraZeneca strategy.

OK, so let's go onto bacterial vaccine. So, one way you can make a bacterial vaccine is just take that sort of complex sugar, sugar coat called the polysaccharide, of the bacteria and use that, which is the way we make the pneumococcal vaccine. Or you can take that polysaccharide coat and then link it to a harmless protein, which makes it even more immunogenic, more likely to induce an excellent immune response, which is the way we make a different pneumococcal vaccine, as well as the meningococcal vaccine, as well as something called the Haemophilus influenzae b vaccine. Or you can just take a protein or a series of proteins from the bacteria, which is basically the way that we make the pertussis, or whooping cough vaccine. And then lastly, you can take just one of the proteins made by the bacteria, a so-called toxin. So, tetanus makes a toxin and diphtheria makes a toxin. You can take that toxin, inactivate it with a chemical, and that's called a toxoid vaccine.

So those are the basic ways to make vaccines. And as we found out over the last hundred years or so, we live 30 years longer because we've been able technologically to do that and to rid ourselves of many of these harmful viruses and bacteria.

Thank you.