An Appreciation for Vaccines, and How Far They Have Come


The first pertussis vaccines were developed and tested in the 1920s and 1930s and were in universal use by the end of the 1940s. And they worked. Dr. James Cherry, a distinguished research professor of pediatrics at David Geffen School of Medicine at the University of California, Los Angeles, and an expert on pertussis who has done extensive research both on the disease and on the vaccines, cites more than 36,000 pertussis deaths from 1926 to 1930 in the United States, most in young infants; from 1970 to 1974, there were 52.

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Answers to Your Vaccine Questions

While the exact order of vaccine recipients may vary by state, most will likely put medical workers and residents of long-term care facilities first. If you want to understand how this decision is getting made, this article will help.

Life will return to normal only when society as a whole gains enough protection against the coronavirus. Once countries authorize a vaccine, they’ll only be able to vaccinate a few percent of their citizens at most in the first couple months. The unvaccinated majority will still remain vulnerable to getting infected. A growing number of coronavirus vaccines are showing robust protection against becoming sick. But it’s also possible for people to spread the virus without even knowing they’re infected because they experience only mild symptoms or none at all. Scientists don’t yet know if the vaccines also block the transmission of the coronavirus. So for the time being, even vaccinated people will need to wear masks, avoid indoor crowds, and so on. Once enough people get vaccinated, it will become very difficult for the coronavirus to find vulnerable people to infect. Depending on how quickly we as a society achieve that goal, life might start approaching something like normal by the fall 2021.


Yes, but not forever. The two vaccines that will potentially get authorized this month clearly protect people from getting sick with Covid-19. But the clinical trials that delivered these results were not designed to determine whether vaccinated people could still spread the coronavirus without developing symptoms. That remains a possibility. We know that people who are naturally infected by the coronavirus can spread it while they’re not experiencing any cough or other symptoms. Researchers will be intensely studying this question as the vaccines roll out. In the meantime, even vaccinated people will need to think of themselves as possible spreaders.

The Pfizer and BioNTech vaccine is delivered as a shot in the arm, like other typical vaccines. The injection won’t be any different from ones you’ve gotten before. Tens of thousands of people have already received the vaccines, and none of them have reported any serious health problems. But some of them have felt short-lived discomfort, including aches and flu-like symptoms that typically last a day. It’s possible that people may need to plan to take a day off work or school after the second shot. While these experiences aren’t pleasant, they are a good sign: they are the result of your own immune system encountering the vaccine and mounting a potent response that will provide long-lasting immunity.

No. The vaccines from Moderna and Pfizer use a genetic molecule to prime the immune system. That molecule, known as mRNA, is eventually destroyed by the body. The mRNA is packaged in an oily bubble that can fuse to a cell, allowing the molecule to slip in. The cell uses the mRNA to make proteins from the coronavirus, which can stimulate the immune system. At any moment, each of our cells may contain hundreds of thousands of mRNA molecules, which they produce in order to make proteins of their own. Once those proteins are made, our cells then shred the mRNA with special enzymes. The mRNA molecules our cells make can only survive a matter of minutes. The mRNA in vaccines is engineered to withstand the cell’s enzymes a bit longer, so that the cells can make extra virus proteins and prompt a stronger immune response. But the mRNA can only last for a few days at most before they are destroyed.


Even so, when I started out in pediatrics, in the 1980s, the DTP was, no question, the shot we least liked giving. Of the shots that we routinely gave, this was the one that kids tended to react to — with fevers, with sore arms, and sometimes, though very rarely, with more serious reactions. “Reactogenic,” we sometimes called it.

The reactions had a lot to do with what went into the vaccine: whole inactivated Bordetella pertussis bacteria. And though bacteria are microscopically small, they are enormous and complex cells compared to viruses, which are just made up of protein and nucleic acid (DNA or RNA). In other words, a whole-cell vaccine contained many different compounds in it that the body might react to — there are more than 3,000 different proteins in the bacterial cell. For diphtheria and tetanus, single “toxoids” were used, inactivated versions of the poisons manufactured by those bacteria, so those components were much less reactogenic.

There were parents who believed that their children had been harmed by the vaccine, and strong sentiment against it in what we would now call the anti-vaccine movement, along with ongoing medical controversy over which problems had been caused by the vaccine and which were coincidences of timing in a vaccine given at 2, 4 and 6 months of age, and then again at around a year and a half.

Since 1999, children in the United States have been vaccinated with DTaP, rather than DTP, with the “a” standing for “acellular.” No more whole cells; these vaccine developers used specific proteins to which the body would manufacture immunity. DTaP shots are significantly less “reactogenic.”

They also tend to be less effective in provoking a long-lasting effective immune response; in a 2019 review, Dr. Cherry wrote that in almost every clinical trial, the whole-cell vaccines were more efficacious than the acellular vaccines. That meant a certain balancing of risks and benefits, and ongoing discussion, as the changeover to DTaP has been linked to recent resurgences in the number of cases, though not necessarily in deaths, and Dr. Cherry argues that the increased number of reported cases may actually be a result of raised awareness and better testing. But even if there is more pertussis around in adults, thanks to the vaccines, this is no longer a deadly disease of young children.


Although a safe adult booster called the Tdap has now been developed, there is still a great deal of pertussis infection in adolescents and adults, and it often goes undiagnosed, even among doctors, because in adults it may not look that different from other coughs and colds.

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