Why Covid-19 Vaccines Take a Whereas to Kick In

A barrage of headlines this week flooded social media, documenting a seemingly worrying case of Covid-19 with a San Diego nurse who fell ill about a week after his first injection of Pfizer’s coronavirus vaccine.

However, experts said the disease is not unexpected: it is known that vaccines take at least a couple of weeks to protect themselves. And getting sick before getting a two-dose vaccination shouldn’t affect the effectiveness of Pfizer’s product, which has blown away with flying colors through late-stage clinical trials.

Reporting that a half-vaccinated person has Covid-19 is “really the equivalent of saying someone went outside without an umbrella and got wet in the middle of a rainstorm,” said Dr. Taison Bell, an intensive care physician at the University of Virginia. Dr. Bell received his first dose of Pfizer’s vaccine on December 15th and will soon be receiving his second shot.

The California nurse, identified as Matthew W. (45) on an ABC10 news report, received his first dose of Pfizer’s vaccine on December 18. Six days later, he started experiencing mild symptoms such as chills and muscle pain and fatigue, according to news reports. He tested positive for the virus the day after Christmas.

Dr. Megan Ranney, an emergency doctor at Brown University, said this shouldn’t be a concern. “So what????” She tweeted Wednesday in response to a Reuters article about the nurse’s illness. “It’s a 2-shot vaccination.” Dr. Ranney received her first dose of Pfizer’s vaccine on December 18th.

Dr. Describing the nurse’s illness as news, Ranney said in an interview that this was a departure from expectations – and that there should be protection about a week after the first dose of vaccine. That is not the case at all.

Vaccines take at least a few days to be protective. Pfizer’s recipe is based on a molecule called messenger RNA, or mRNA, which once injected into human cells and instructs them to make a coronavirus protein called Spike. None of these components are infectious or can cause Covid-19. But they act as coronavirus mimickers, teaching the body to recognize the real virus and defeat it should it ever occur.

It is believed that the production of spikes occurs within hours of the first shot. However, the body needs at least a few days to memorize the material before it can break down its entire arsenal of defenses against the virus. Immune cells take this time to examine the protein, then mature, multiply, and sharpen their spike-spotting reflexes.

Data from Pfizer’s clinical trials suggests that the vaccine could protect its recipients from disease about a week or two after the first injection. A second shot of mRNA, released three weeks after the first, helps the immune cells incorporate the most important features of the virus into memory and speed up the protection process.

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Answers to your vaccine questions

With a coronavirus vaccine spreading out of the US, here are answers to some questions you may be wondering about:

    • 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. Here’s why. The coronavirus vaccines are injected deep into the muscles and stimulate the immune system to produce antibodies. This seems to be sufficient protection to protect the vaccinated person from disease. What is not clear, however, is whether it is possible for the virus to bloom in the nose – and sneeze or exhale to infect others – even if antibodies have been mobilized elsewhere in the body to prevent that vaccinated person gets sick. The vaccine clinical trials were designed to determine whether people who were vaccinated are protected from disease – not to find out whether they can still spread the coronavirus. Based on studies of flu vaccines and even patients infected with Covid-19, researchers have reason to hope that people who are vaccinated will not spread the virus, but more research is needed. In the meantime, everyone – including those who have been vaccinated – must imagine themselves as possible silent shakers and continue to wear a mask. Read more here.
    • 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 in your arm feels no different than any other vaccine, but the rate of short-lived side effects seems to be higher than with the flu shot. Tens of thousands of people have already received the vaccines, and none of them have reported serious health problems. The side effects, which can be similar to symptoms of Covid-19, last about a day and are more likely to occur after the second dose. Early reports from vaccine trials suggest that some people may need to take a day off because they feel lousy after receiving the second dose. In the Pfizer study, around half developed fatigue. Other side effects occurred in at least 25 to 33 percent of patients, sometimes more, including headache, chills, and muscle pain. While these experiences are not pleasant, they are a good sign that your own immune system is having a potent response to the vaccine that provides 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 moment, 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 hold for a few days at most before it is destroyed.

The California nurse’s illness schedule falls well within the post-vaccination vulnerability window, said Dr. Ranney. It’s also very likely that he discovered the virus around the time he got the shot, maybe even before that. People may notice symptoms of Covid-19 between two and 14 days after the coronavirus emerges, if they ever have symptoms.

A similar situation appears to have developed recently with Mike Harmon, the Kentucky state chartered accountant, who tested positive for the virus this week the day after receiving his first dose of an unspecified coronavirus vaccine.

“It appears that I was unknowingly exposed to the virus and got infected either shortly before or after receiving the first dose of the vaccine on Monday,” Harmon said in a statement. Mr Harmon reiterated his “full confidence in the vaccine itself and the need for as many people to receive it as soon as possible”.

Jerica Pitts, a Pfizer spokeswoman, noted that the vaccine’s protective effect “is significantly increased after the second dose, supporting the need for a two-dose series”.

“People may have contracted an illness before or immediately after being vaccinated,” she said.

Pfizer’s vaccine, when given in its full two-dose regimen, was found to be 95 percent effective in preventing symptomatic cases of Covid-19 – a figure that is very welcome news given the rise Coronavirus case numbers was celebrated. Still, a small percentage of people who are not protected after vaccination remain, said Dr. Ranney. “There is no such thing as a vaccine that is 100 percent effective.”

It is also unclear how well Pfizer’s vaccine can protect against asymptomatic infections, or whether it significantly limits the ability of the coronavirus to spread from person to person. This means that measures such as masking and distancing remain essential even after a full vaccination.

Data collected by Pfizer during its late-stage clinical trials suggested that the vaccine might provide at least some protection after a single dose. However, the study was not intended to specifically test how effective a one-shot regimen would be.

Dr. Krutika Kuppalli, an infectious disease doctor at the Medical University of South Carolina, said some of her colleagues tested positive shortly after their first shots. “None of this surprises me given the prevalence of the cases now,” she said. Given the expected delay in vaccination effect, “this should not be viewed as a vaccination failure”. Dr. Kuppalli, who received her first dose of Pfizer’s vaccine on Dec. 15, added that taking Covid-19 between vaccine doses shouldn’t stop anyone from getting a second shot after consulting a health care provider.

In the past few weeks, more than 2.7 million people in the US have received their first dose of Pfizer’s vaccine, or a similar shot of Moderna. Both vaccines require a second injection – and as they’re made available to more people, it’s important to keep clear communication about how and when vaccines work, said Dr. Bell.

“For now we should stick to the dosages as the experiments were carried out,” he said. “This is what will bring you maximum effectiveness.”

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