Scientists developed vaccines less than a year after Covid-19 was identified, reflecting a remarkable advance in vaccine technology. Advances in vaccine distribution, however, are a different story.

Many questions that arose decades ago when vaccines were introduced are still debated today. How should local and federal authorities coordinate? Who should be vaccinated first? What should officials do about resistance in the communities? Should the most affected locations be prioritized? Who should pay?

Some answers can be found in the successes and failures of vaccine campaigns over the past two centuries.

When scientist Edward Jenner discovered that people infected with cowpox became immune to smallpox in 1796, doctors in England went from town to town, deliberately spreading cowpox by scratching infected material into people’s arms.

The rollout worked at the local level, but how could it be distributed to people in remote areas like America, where smallpox had ravaged the population? In 1803 the Spanish government put 22 orphans on a ship to their South American territories. Senior doctor Francisco Xavier de Balmis and his team injected two of the boys with cowpox and then, as soon as cowpox wounds developed, they would take material from the wounds and scratch it into the arms of two more boys.

When the team got to the Americas, only one boy was infected, but that was enough. The distribution of vaccines in the Spanish territories was unsystematic, but eventually members of the Spanish expedition worked with local political, religious and medical authorities to set up vaccination clinics. More than 100,000 people in Mexico received free vaccinations by 1805, according to a magazine article in the Bulletin of the History of Medicine: “The World’s First Vaccination Campaign.”

By the 20th century, when scientists figured out how to store and mass-produce the smallpox vaccine, outbreaks had generally been contained.

However, a 1947 outbreak in New York City, just before an Easter Sunday parade on a warm weekend, was a major problem. The city’s then health commissioner, Israel Weinstein, urged everyone to be vaccinated, even if they were vaccinated as children. Posters all over town warned, “Be safe. Be sure. Get vaccinated! “

The rollout was quick and well orchestrated. Volunteer and professional health care providers went to schools and delivered vaccines to students. At the time, the public had a strong reliance on the medical community, and the modern anti-vaccination movement barely existed. More than six million New Yorkers were vaccinated in less than a month, and the city recorded only 12 infections and two deaths.

On April 12, 1955, the U.S. government approved the first Dr. Jonas Salk developed a vaccine against poliomyelitis after scientists announced that day that it was 80 to 90 percent effective.

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Answers to your vaccine questions

If I live in the US, when can I get the vaccine?

While the exact order of vaccine recipients may vary from state to state, most doctors and residents of long-term care facilities will come first. If you want to understand how this decision is made, this article will help.

When can I get back to normal life after the vaccination?

Life will only get back to normal once society as a whole receives adequate protection against the coronavirus. Once countries have approved a vaccine, they can only vaccinate a few percent of their citizens in the first few months. The unvaccinated majority remain susceptible to infection. A growing number of coronavirus vaccines show robust protection against disease. However, it is also possible that people spread the virus without knowing they are infected because they have mild or no symptoms. Scientists don’t yet know whether the vaccines will also block the transmission of the coronavirus. Even vaccinated people have to wear masks for the time being, avoid the crowds indoors and so on. Once enough people are vaccinated, it becomes very difficult for the coronavirus to find people at risk to become infected. Depending on how quickly we as a society achieve this goal, life could approach a normal state in autumn 2021.

Do I still have to wear a mask after the vaccination?

Yeah, but not forever. The two vaccines that may be approved this month clearly protect people from contracting Covid-19. However, the clinical trials that produced 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 with the coronavirus can spread it without experiencing a cough or other symptoms. Researchers will study this question intensively when the vaccines are introduced. In the meantime, self-vaccinated people need to think of themselves as potential spreaders.

Will it hurt What are the side effects?

The vaccine against Pfizer and BioNTech, like other typical vaccines, is delivered as a shot in the arm. The injection is no different from the ones you received before. Tens of thousands of people have already received the vaccines, and none of them have reported serious health problems. However, some of them have experienced short-lived symptoms, including pain and flu-like symptoms that usually last a day. It is possible that people will have to plan to take a day off or go to school after the second shot. While these experiences are not pleasant, they are a good sign: they are the result of your own immune system’s encounter with the vaccine and a strong response that ensures lasting immunity.

Will mRNA vaccines change my genes?

No. Moderna and Pfizer vaccines use a genetic molecule to boost the immune system. This molecule, known as mRNA, is eventually destroyed by the body. The mRNA is packaged in an oily bubble that can fuse with a cell, allowing the molecule to slide inside. The cell uses the mRNA to make proteins from the coronavirus that can stimulate the immune system. At any given point in time, each of our cells can contain hundreds of thousands of mRNA molecules that they produce to make their own proteins. As soon as these proteins are made, our cells use special enzymes to break down the mRNA. The mRNA molecules that our cells make can only survive a few minutes. The mRNA in vaccines is engineered to withstand the cell’s enzymes a little longer, so the cells can make extra viral proteins and trigger a stronger immune response. However, the mRNA can last a few days at most before it is destroyed.

The next day, the New York Times reported in a front-page headline: “Supply is said to be low in time, but production is accelerating.”

State and local health officials were responsible for introducing children who were at greatest risk of developing the disease.

“Young African American children were hit but were not at the top of the priority list because of the social conditions at the time,” said Dr. René F. Najera, editor of the History of Vaccines project at the College of Physicians in Philadelphia. Dr. Noting that it was difficult for parents in worker jobs to take the time to be in harmony with children in clinics, Najera said, “You keep seeing this, history repeats itself.”

Shortly after the rollout began, the program was put on hold after reports that children had developed polio in the arms they received the vaccination in rather than the legs, which was more typical of the disease.

More than 250 cases of polio have been traced back to faulty vaccines caused by a manufacturing error from one of the drug makers involved in the effort, Cutter Laboratories in California, according to the Centers for Disease Control and Prevention.

The so-called Cutter incident resulted in stricter regulatory requirements and the introduction of the vaccine continued in the fall of 1955. The vaccine prevented thousands of debilitating disease cases, saved lives and ultimately ended the annual epidemic threat in the United States.

The H1N1 influenza virus, which originated in Mexico, appeared in the spring of 2009, not the typical flu season.

By late summer, it was clear that the virus was causing fewer deaths than many seasonal strains of flu and that some of the early reports from Mexico were exaggerated. That was one of the main reasons many Americans avoided the flu vaccine when it finished that fall. It wasn’t just the anti-vaccination movement, though that was a factor.

The H1N1 virus was harsh on children and young adults and appeared to have a disproportionately high death rate in pregnant women. Because of these factors, the first groups to be vaccinated after healthcare workers were those at the highest risk of complications, pregnant women and children.

The last group eligible for the vaccine were healthy people over 65 who were the least likely to get the vaccine because they appeared to have some resistance to it.

Donald G. McNeil Jr. contributed to the coverage.