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Las vacunas de Pfizer y Moderna podrían generar una inmunidad duradera, según científicos

Las vacunas fabricadas por Pfizer-BioNTech y Moderna generan una reacción inmunitaria persistente en el organismo que puede proteger contra el coronavirus durante años, informó el lunes un grupo de científicos.

Los hallazgos se suman a la creciente evidencia de que la mayoría de las personas inmunizadas con las vacunas de ARNm podrían no necesitar refuerzos, siempre y cuando el virus y sus variantes no evolucionen mucho más allá de sus formas actuales, algo que no está garantizado. Es posible que las personas que se recuperaron de COVID-19 antes de ser vacunadas no necesiten refuerzos incluso si el virus realiza una transformación significativa.

“Es una buena señal de lo durable que es nuestra inmunidad proveniente de esta vacuna”, dijo Ali Ellebedy, inmunólogo de la Universidad de Washington en Saint Louis que dirigió el estudio, publicado en la revista Nature.

El estudio no incluyó a la vacuna fabricada por Johnson & Johnson, sin embargo, el doctor Ellebedy dijo que esperaba que la respuesta inmunitaria sea menos durable que la que producen las vacunas de ARN mensajero.

Ellebedy y sus colegas reportaron el mes pasado que en quienes sobreviven a la COVID-19, las células inmunitarias que reconocen al virus permanecen inactivas (durmientes) en la médula ósea durante al menos ocho meses después de la infección. Un estudio de otro equipo indicó que las llamadas células B de memoria siguen madurando y fortaleciéndose durante al menos un año tras la infección.

Los investigadores, con fundamento en esos hallazgos, sugirieron que la inmunidad podría durar por años y tal vez toda la vida en las personas que contrajeron el coronavirus y luego fueron vacunadas. Pero no quedó muy claro si es posible conseguir un efecto tan duradero solo con la vacunación.

El equipo de Ellebedy buscó resolver esa pregunta al examinar la fuente de las células de memoria: los nódulos linfáticos, donde las células inmunitarias se entrenan para reconocer y combatir el virus.

Después de una infección o la vacunación, se forma una estructura especializada llamada centro germinal en los ganglios linfáticos. Esta estructura es una suerte de escuela de élite para las células B, un campo de entrenamiento donde se vuelven cada vez más sofisticadas y aprenden a reconocer un conjunto diverso de secuencias genéticas virales.

Es más probable que estas células logren frustrar a las variantes del virus que puedan surgir si disponen de más tiempo y rango para practicar.

“Todos se enfocan siempre en la evolución del virus; esto muestra que las células B están haciendo lo mismo”, dijo Marion Pepper, inmunóloga de la Universidad de Washington en Seattle. “Y va a proteger contra la evolución en curso del virus, lo cual es realmente alentador”.

Después de contraer el coronavirus, se forma el centro germinal en los pulmones. Pero después de la vacunación, la educación de las células sucede en los nódulos linfáticos de las axilas, al alcance de los investigadores.

Ellebedy y sus colegas reclutaron a 41 personas, incluidas ocho con antecedentes de infección por el virus, que fueron inmunizadas con dos dosis de la vacuna Pfizer-BioNTech. De 14 de estas personas, el equipo extrajo muestras de los ganglios linfáticos a las tres, cuatro, cinco, siete y 15 semanas después de la primera dosis.

Ese laborioso trabajo es lo que hace que este sea un “estudio heróico”, comentó Akiko Iwasaki, inmunólogo de Yale. “Este tipo de análisis cuidadoso de series de tiempo en humanos es muy difícil de realizar”.

El equipo de Ellebedy encontró que a las 15 semanas de recibir la primera dosis de la vacuna, el centro germinal seguía altamente activo en los 14 participantes y que la cantidad de células de memoria capaces de reconocer al coronavirus no había disminuido.

“Que las reacciones continuaran casi cuatro meses después de la vacunación, es una señal muy muy buena”, comentó Ellebedy. Los centro germinales suelen tener su máxima expresión una o dos semanas después de la inmunización y luego declinan.

“Por lo general no suele quedar mucho después de cuatro a seis semanas”, dijo Deepta Bhattacharya, inmunólogo de la Universidad de Arizona. Pero los centros germinales estimulados por las vacunas de ARNm “siguen activas a los meses y no declinan mucho en la mayoría de las personas”.

Bhattacharya indicó que la mayor parte de lo que los científicos saben sobre la persistencia de los centros germinales proviene de la investigación con animales. El nuevo estudio es el primero en mostrar lo que sucede en las personas después de la vacunación.

Los resultados sugieren que una gran mayoría de las personas vacunadas estarán protegidas a largo plazo, al menos contra las variantes de coronavirus existentes. Pero los adultos mayores, las personas con sistemas inmunitarios débiles y aquellos que toman medicamentos inmunosupresores puede que necesiten refuerzos; Es posible que las personas que sobrevivieron a la COVID-19 y luego fueron inmunizadas nunca los necesiten.

Es difícil predecir con exactitud cuánto durará la protección de las vacunas de ARN mensajero. Si no existieran las variantes que esquivan a la inmunidad, esta podría durar en teoría toda la vida. Pero el virus claramente sigue evolucionando.

“Cualquier necesidad de un refuerzo sería a causa de una variante, no de un declive de la inmunidad”, dijo Bhattacharya. “No veo que eso llegue a suceder”.

Las personas que se infectaron con el coronavirus y luego se inmunizaron experimentan un aumento importante en sus niveles de anticuerpos, muy probablemente porque sus células B de memoria, que producen anticuerpos, tuvieron muchos meses para evolucionar antes de la vacunación.

La buena noticia: la vacuna de refuerzo probablemente tendrá el mismo efecto que una infección previa en personas inmunizadas, dijo Ellebedy. “Si les brindas otra oportunidad de participar, responderán de forma masiva”, dijo, refiriéndose a las células B de memoria.

En lo que respecta a reforzar el sistema inmunológico, la vacunación es “probablemente mejor” que recuperarse de la infección real, dijo. Otros estudios han sugerido que el repertorio de células B de memoria que se producen después de la vacunación es más diverso que el generado por la infección, lo que sugiere que las vacunas protegen mejor contra variantes que la inmunidad natural por sí sola.

Ellebedy dijo que los resultados también sugieren signos de una reacción inmunitaria persistente producidos por las vacunas de ARNm, en lugar de por aquellas más tradicionales, como la de Johnson & Johnson.

Pero esa es una comparación injusta, ya que la vacuna de Johnson & Johnson se administra en una sola dosis, dijo Iwasaki: “Es probable que si la J & J tuviera una segunda dosis, podría inducir el mismo tipo de respuesta”.

Apoorva Mandavilli es reportera del Times y se enfoca en ciencia y salud global. En 2019 ganó el premio Victor Cohn a la Excelencia en Reportaje sobre Ciencias Médicas. @apoorva_nyc

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Health

Vacunas para la COVID-19: ¿debo ponerme la segunda dosis?

However, the agency warned unvaccinated people that they are at greater risk – and should continue to wear face masks – if they go to the movies indoors, dine in a restaurant or bar, take high-intensity exercise classes indoors, or sing in a restaurant choir indoors . Rochelle Walensky, the director of the CDC, noted that the risk of spreading the virus indoors increases almost 20 times.

Updated

May 13, 2021 at 7:22 AM ET

And even for vaccinated people, he stated, “Until there are no more vaccinated people and we continue with more than 50,000 cases a day, wearing masks indoors provides additional protection.”

There are good reasons to be careful. More than half of the population, including children, are still not immunized. It is not known whether immunized people can become infected with the virus and have no symptoms and then accidentally spread it to other vulnerable people. Not everyone who wants to get vaccinated can do so for logistical or health reasons, and vaccines may not fully protect people with immunodeficiency.

Even if approved vaccines produce a stronger immune response than natural infections, we still don’t know how long their protection will last. The Excelsior Pass I was given in New York State confirms my vaccination status but will expire in mid-August, six months after my second dose, when I may need a booster to maintain my immunity.

Speaking of which, no one should stop getting that second dose of Pfizer or Moderna vaccines. While taking a few weeks to get the second is probably not all that important, the immune response is relatively weak after a dose and could leave people vulnerable, especially to the more virulent variants that are now floating around.

Two doses are 90 percent effective at preventing infection, and that protection is likely to last much longer. You should be scheduled for the second dose when you sign up for the first dose or when you receive it.

Some people hesitate to take the second dose because they have heard that the side effects can be uncomfortable. No matter how uncomfortable it may be, the vaccine’s side effects are brief and nowhere near as severe or persistent as the disease it protects you from. Even after recovering from a mild case of COVID-19, annoying imprints such as disorientation and chronic fatigue can be left behind.

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Business

El futuro de las vacunas depende de algo que escasea: los monos de laboratorio

Mark Lewis was dying to find monkeys. Millions of lives were at risk around the world.

Lewis, CEO of Bioqual, was responsible for supplying the lab overalls to pharmaceutical companies like Moderna and Johnson & Johnson that animals needed to develop their COVID-19 vaccines. Last year, when the coronavirus swept through the United States, almost no monkeys were bred around the world specifically bred for this purpose.

In the absence of a supply of monkeys for scientific purposes, which can cost more than $ 10,000 each, nearly a dozen companies had to do everything possible to find these animal species at the height of the pandemic.

“We lost jobs because we couldn’t take care of the animals during that time,” said Lewis.

The world needs monkeys, primates with very human DNA, to develop vaccines against COVID-19. However, a recent ban on the sale of wild animals from China, the main supplier of laboratory animals, has exacerbated a global shortage caused by unexpected demand due to the pandemic.

The recent shortage has rekindled the debate over the creation of a strategic monkey reserve in the United States, an emergency reserve that resembles the government-maintained oil and grain reserves.

As new variants of the coronavirus threaten to obsolete the current amount of vaccines, scientists are looking for new monkey sources and the US is reassessing its reliance on China, a rival with its own biotech ambitions.

The pandemic has cleared China’s control over the supply of emergency products, including the masks and medicines the United States needs in a crisis.

American scientists have searched both private and government-funded facilities in Southeast Asia and Mauritius, a tiny island in Southeast Africa, for their preferred subjects, the rhesus and cynomolgus macaques, also known as long-tailed macaques.

However, no country can compensate for the supply from China. Prior to the 2019 pandemic, China supplied more than 60 percent of the 33,818 primates, mostly cynomolgus macaques, that were imported into the United States. This is based on analyst estimates based on data from the Centers for Control and Management. Disease prevention.

The United States has up to 25,000 laboratory monkeys – mostly pink-faced rhesus monkeys – in its seven primate centers. Since the pandemic began, between 600 and 800 of these animals have been the subject of coronavirus research.

According to scientists, monkeys are ideal samples to study COVID-19 vaccines before testing on humans. Primates share more than 90 percent of our DNA and, thanks to their biology, can be tested with nasal swabs and scanned lungs. Scientists say finding a substitute for testing COVID-19 vaccines is nearly impossible, despite drugs like dexamethasone, the steroid ex-president Donald Trump who self-medicated, have been tested on hamsters.

In the past, the United States turned to India for supplying rhesus monkeys. In 1978 India stopped exporting after the Indian press reported that the overalls were being used for military testing in the United States. Pharmaceutical companies were looking for an alternative.

In the end they reached China.

The pandemic disrupted the decades-long relationship between American scientists and Chinese suppliers.

“The closure of the Chinese market forced everyone to turn to less available animals,” said Lewis.

For years, several airlines, including large American ones, have also refused to transport animals used in medical research because animal rights activists oppose it.

Meanwhile, the price of a cynomolgus monkey has more than doubled year over year and is well over $ 10,000, according to Lewis. Scientists researching cures for other diseases such as Alzheimer’s and AIDS say their work has been delayed as coronavirus researchers prioritize animals.

Due to the shortage, more and more American scientists have begun to urge the government to ensure steady supplies for the animals.

Skip Bohm, assistant director and chief veterinarian of the National Primate Research Center at Tulane University outside of New Orleans, noted that the strategic ape sanctuary debate among directors of the national primate research centers began about 10 years ago. However, due to the time and money involved in starting a breeding program, a reserve was never created.

“Our idea was something like a strategic oil reserve in the sense that there is a lot, a lot of fuel that is only used in an emergency,” said Bohm.

With the discovery of new variants of the virus that could resume the race for a vaccine, scientists say the government must take immediate action to create the reserve.

“The strategic monkey reserve is exactly what we need to fight COVID and we just don’t have it,” said Keith Reeves, principal researcher at Harvard Medical School’s Center for Virology and Vaccine Research.

However, a strong strategic reserve may not be able to meet stratospheric demand for laboratory animals, researchers in China have found. Even with a reserve of around 45,000 monkeys under state control, researchers from China say they are struggling with shortages.

Researchers often collect hundreds of samples from a single monkey whose tissues can be frozen for years and examined over long periods of time. Scientists say they make the most of every animal, but monkeys infected with COVID-19 cannot return to live with other healthy animals and must ultimately be euthanized.

In January, Shen Weiguo, CEO of Shanghai Tech Venture Capital Group, told local lawmakers that the city’s three major biomedical companies needed and did not have 2,750 research monkeys, according to a media report last year. The deficit is set to grow 15 percent annually for the next five years, Shen said.

Hubei Topgene Biotechnology breeds monkeys for its own research and for export. The US used to be the main export destination, but currently the company does not have enough animals to conduct its own experiments, said Yan Shuo, sales director.

“Now it’s not even about money,” said Yan. “We don’t even have monkeys to sell abroad.”

The United States has seven primate research centers nationwide where animals, when not involved in the research, live in colonies with access to nature and enrichment activities. The facilities are affiliated with universities and funded by the National Institutes of Health. For years, animal rights activists have accused the centers of abuse, such as separating boys and mothers.

Matthew R. Bailey, president of the National Association for Biomedical Research, said he was preparing to introduce the monkey shortage problem to the Biden administration. Bailey mentioned that China’s decision to halt exports at the start of the pandemic “was likely a prudent emergency maneuver,” but suggested that China could export again now that the virus is known to be spreading.

The Chinese Foreign Ministry said the ban has no specific targets, species, or countries.

“If the international situation improves and conditions for import and export are met, China will carefully consider resuming imports and exports and other related activities,” the ministry said in a statement.

Experts said the United States had some responsibility for not having enough research monkeys.

Budgets for national primate centers have been stable or declining for more than a decade. Koen Van Rompay, an infectious disease expert at the California National Primate Research Center, said the federal government asked the center to expand its breeding colonies about ten years ago but did not provide further funding, so the colony ended up declining.

“In several cases we have given birth controls to our women,” said Van Rompay. “So fewer babies were born in the spring.”

In a panel hosted by the National Institutes of Health in December 2018, scientists discussed the challenges facing American primate care. It was then determined that “if China decides to shut the faucet, we will be in serious trouble,” said Jeffrey Roberts, assistant director of the California National Primate Research Center.

Participants “agreed that the need to breed cynomolgus macaques in the country is essential and, if not met, could jeopardize biomedical research in the United States as a whole,” said a session report. “They stressed that it may be too late to meet these needs, but it will certainly be in a few months.”

Amber Wang and Elsie Chen helped with the investigation.

Sui-Lee Wee is the New York Times correspondent in Singapore. She has covered China for nearly a decade, writing on social issues, gender, genetic surveillance, health care, and the interface between demographics and the economy. @ Suilee