Risk factors and disease profile of post-vaccination SARS-CoV-2 infection in UK users of the COVID Symptom Study app: a prospective, community-based, nested, case-control study

‘COVID-19 vaccines show excellent efficacy in clinical trials and effectiveness in real-world data, but some people still become infected with SARS-CoV-2 after vaccination. This study aimed to identify risk factors for post-vaccination SARS-CoV-2 infection and describe the characteristics of post-vaccination illness.

‘To minimise SARS-CoV-2 infection, at-risk populations must be targeted in efforts to boost vaccine effectiveness and infection control measures. Our findings might support caution around relaxing physical distancing and other personal protective measures in the post-vaccination era, particularly around frail older adults and individuals living in more deprived areas, even if these individuals are vaccinated, and might have implications for strategies such as booster vaccinations.’

Read here (The Lancet, Nov 1, 2021)

View John Campbell’s video on “Severe illness after vaccination” on the above here.

Indian Covid mutant more contagious, but not vaccine resistant: Top WHO scientist

“Surge in India increases chances of more dangerous variants emerging. Prelim data shows that Indian variant is more contagious. There is heterogeneity in India in terms of spread of Covid-19. WHO is concerned about number of cases and deaths in India. Globally, cases and deaths have plateaued, not in South Asia. South East Asia is seeing case rise owing to India. Overall numbers hide what is going on, need to go deeper in state, local level data,” she said.

‘Speaking on efficacy of vaccines available in India, she assured, “There is no enough data to show that double mutant is vaccine resistant. All the available vaccines today in India and elsewhere prevent severe disease and death even if you get up the infection. You are not going to end up in the ICU critically ill. The message is take the vaccine whichever is available and you eligible for it. If your turn is there, please take it.”

Read here (Yahoo, May 10, 2021)

How a small city in Brazil may reveal how fast vaccines can curb Covid-19

‘The city of Serrana in Brazil is a living experiment. The picturesque place, surrounded by sugarcane fields, is nestled in the southeast of one of the countries hit hardest by COVID-19. By the end of March, daily deaths in Brazil surged to 3,000 on average a day, a high in a pandemic that has claimed more than 405,000 lives there — the second worst death toll of any country in the world behind only the United States. And as vaccines slowly trickle into the country, only about 15 percent of the population has gotten at least one shot.

‘Except in Serrana. There, nearly all the adults have gotten their shots. What happens next in this city could provide a glimpse of what the future of the pandemic could be — not only in Brazil but across the globe as vaccinations pick up.’

Read here (Science News, May 5, 2021)

Vaccinations, increasing Covid-19 cases, and the Peltzman effect

‘How security measures and regulations meant to protect, actually increase risky behaviour in the public, and how not to become a stereotype...

‘So, what has this got to do with Covid-19 vaccinations? This is where Dr Puri and his message come in. Pakistan's Prime Minister Imran Khan reportedly tested positive with the coronavirus a few days after being vaccinated.  People assume, wrongly, that vaccination (especially after the first dose) makes you invincible and you can get back to partying and a pre-Covid-19 normal life. Not true. The immunity builds up only a few weeks after the second dose. Also, immunity is not absolute. You can still get infected after being vaccinated, just like you could die in a car accident even though you are wearing a seatbelt. If you wear a seatbelt, you should not drive recklessly. Similarly, if you are vaccinated, you should not behave recklessly. You need to follow the basics—wear a mask, maintain social distance and wash your hands. Furthermore, current vaccines may not be able to protect you against future variants of the virus.

‘So why take the vaccine? Because it does reduce the risk of you getting the virus, and more importantly the risk of dying is significantly reduced. But just like the seat belt can't protect you if you drive like an idiot, the vaccine won’t protect you if you behave like one. Sometimes a seat belt doesn't protect you even if you are driving carefully (because some other idiot is driving recklessly) or you are an innocent bystander. It's the same case with the vaccine. Some other idiot can get you infected, even if you are an innocent bystander. Hence, please don’t believe that being vaccinated makes you superhuman.’

Read here (Forbes India, Apr 8, 2021) 

Can vaccinated people transmit COVID-19? The answer will be key to ending the pandemic

‘There’s been positive news about how effective the vaccines might be in preventing transmission—but as several experts note, some studies that have been made public so far are inconclusive. Until we have a better answer on transmission, social distancing, hand hygiene, testing, and mask wearing will remain important in the fight to limit and eventually end the pandemic.

‘A recent, unpublished Israeli study showed a nearly 90 percent reduction in infections among the vaccinated population. Wired magazine writer Megan Molteni noted that the media framing of the study may have been overly optimistic. While the headlines about this unpublished study were wildly enthusiastic, the reality is more nuanced.  “Israel finds BioNTech/Pfizer vaccine reduced virus transmission,” read one headline. But Eric Topol, a professor of molecular medicine at Scripps Research, told Wired he was skeptical about drawing any conclusions about the extent to which the Pfizer vaccine cut transmission rates. He told the magazine that to accurately study asymptomatic transmission, both vaccinated and unvaccinated people should be regularly tested. “The testing rates were such a hodgepodge, I don’t know you can make any conclusions about how much the vaccine cut transmission in Israel, let alone assigning a number as concrete as 89.4 percent,” he told Molteni.’

Read here (Bulletin of the Atomic Scientists, March 9, 2021)

Can Covid vaccines stop transmission? Scientists race to find answers

‘Controlling the pandemic will require shots that prevent viral spread, but that feature is difficult to measure...

‘Preliminary analyses suggest that at least some vaccines are likely to have a transmission-blocking effect. But confirming that effect — and how strong it will be — is tricky because a drop in infections in a given region might be explained by other factors, such as lockdowns and behaviour changes. Not only that, the virus can spread from asymptomatic carriers, which makes it hard to detect those infections.

“These are among the hardest types of studies to do,” says Marc Lipsitch, an infectious-disease epidemiologist at the Harvard T. H. Chan School of Public Health in Boston, Massachusetts. “All of us are out there, hungrily trying to see what we can get out of little bits of data that do come out,” he says. Results from some studies are expected in the next few weeks.’

Read here (Nature, Feb 19, 2021)

Can you still transmit Covid-19 after vaccination?

‘In fact, most vaccines don't fully protect against infection, even if they can block symptoms from appearing. As a result, vaccinated people can unknowingly carry and spread pathogens. Occasionally, they can even start epidemics. 

"Effective" or "sterilising" immunity: There are two main types of immunity you can achieve with vaccines. One is so-called "effective" immunity, which can prevent a pathogen from causing serious disease, but can't stop it from entering the body or making more copies of itself. The other is "sterilising immunity", which can thwart infections entirely, and even prevent asymptomatic cases. The latter is the aspiration of all vaccine research, but surprisingly rarely achieved.

What type of immunity do the Covid-19 vaccines provide? "In a nutshell we don't know, because they’re too new," says Neal. So far, the available Covid-19 vaccines have not been judged primarily on their ability to prevent transmission – though this is now being evaluated as a secondary endpoint for many of them. Instead, their efficacy was assessed by whether they could prevent symptoms from developing. "This means that we set our targets kind of pragmatically," says Danny Altmann, professor of immunology at Imperial College London.’

Read here (BBC, Feb 4, 2021)

Vaccines need not completely stop Covid transmission to curb the pandemic

‘Influenza may provide the best blueprint of what to expect going forward. The most common flu vaccine—the inactivated virus—is not “truly sterilizing because it doesn’t generate local immune response in the respiratory tract,” Crowcroft says. This fact, coupled with low immunization rates (often shy of 50 percent among adults) and the influenza virus’s ability to infect and move between multiple species, enables it to constantly change in ways that make it hard for our immune system to recognize. Still, depending on the year, flu vaccines have been shown to reduce hospitalizations among older adults by an estimated 40 percent and intensive care admissions of all adults by as much as 82 percent.

‘Research on seasonal coronaviruses suggests that SARS-CoV-2 could similarly evolve to evade our immune systems and vaccination efforts, though probably at a slower pace. And data remain mixed on the relationship between symptoms, viral load and infectiousness. But ample precedent points to vaccines driving successful containment of infectious diseases even when they do not provide perfectly sterilizing immunity. “Measles, diphtheria, pertussis, polio, hepatitis B—these are all epidemic-prone diseases,” Crowcroft says. “They show that we don’t need 100 percent effectiveness at reducing transmission, or 100 percent coverage or 100 percent effectiveness against disease to triumph over infectious diseases.”

Read here (Scientific American, Jan 18, 2021)

UK ready for roll-out but Pfizer CEO 'not certain' if vaccine stops transmission

‘Days after getting back-to-back approvals from the United Kingdom (UK) and Bahrain health regulatory bodies for the emergency use of its coronavirus vaccine, Pfizer Inc CEO Albert Bourla is now "not certain" if the company-made vaccine to prevent the Covid-19 can actually stop the transmission of the infection. The basic.

‘...during an interview with NBC's Lestor Holt, Pfizer CEO, when asked whether a person can still transmit the virus after vaccination, said he was "not certain". "I think this is something that needs to be examined. We are not certain about that right now with what we know," he was quoted as saying.’

Read here (India Today, Dec 6, 2020)

Moderna's chief medical officer says that vaccine trial results only show that they prevent people from getting sick — not necessarily that recipients won't still be able to transmit the virus

‘Moderna Chief Medical Officer Tal Zaks told Axios that the public should not "over-interpret" the vaccine trial results to assume life could go back to normal after adults are vaccinated. "They do not show that they prevent you from potentially carrying this virus transiently and infecting others," Zaks told Axios.  While he believes, based on the science, that it's likely that vaccine does prevent transmission, but said there's still no solid proof of that yet. "I think it's important that we don't change behavior solely on the basis of vaccination," he said.’

Read here (Business Insider, Nov 24, 2020)