Virus World
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Virus World
Virus World provides a daily blog of the latest news in the Virology field and the COVID-19 pandemic. News on new antiviral drugs, vaccines, diagnostic tests, viral outbreaks, novel viruses and milestone discoveries are curated by expert virologists. Highlighted news include trending and most cited scientific articles in these fields with links to the original publications. Stay up-to-date with the most exciting discoveries in the virus world and the last therapies for COVID-19 without spending hours browsing news and scientific publications. Additional comments by experts on the topics are available in Linkedin (https://www.linkedin.com/in/juanlama/detail/recent-activity/)
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Millions Are Skipping Their Second Doses of Covid-19 Vaccines - The New York Times

Millions Are Skipping Their Second Doses of Covid-19 Vaccines - The New York Times | Virus World | Scoop.it

Nearly 8 percent of those who got initial Pfizer or Moderna shots missed their second doses. State officials want to prevent the numbers from rising. Millions of Americans are not getting the second doses of their Covid-19 vaccines, and their ranks are growing. More than five million people, or nearly 8 percent of those who got a first shot of the Pfizer or Moderna vaccines, have missed their second doses, according to the most recent data from the Centers for Disease Control and Prevention. That is more than double the rate among people who got inoculated in the first several weeks of the nationwide vaccine campaign. Even as the country wrestles with the problem of millions of people who are wary about getting vaccinated at all, local health authorities are confronting an emerging challenge of ensuring that those who do get inoculated are doing so fully. The reasons vary for why people are missing their second shots. In interviews, some said they feared the side effects, which can include flulike symptoms. Others said they felt that they were sufficiently protected with a single shot.  Those attitudes were expected, but another hurdle has been surprisingly prevalent. A number of vaccine providers have canceled second-dose appointments because they ran out of supply or didn’t have the right brand in stock. Walgreens, one of the biggest vaccine providers, sent some people who got a first shot of the Pfizer or Moderna vaccine to get their second doses at pharmacies that only had the other vaccine on hand. Several Walgreens customers said in interviews that they scrambled, in some cases with help from pharmacy staff, to find somewhere to get the correct second dose. Others, presumably, simply gave up.

 

From the outset, public health experts worried that it would be difficult to get everyone to return for a second shot three or four weeks after the first dose. It is no surprise that, as vaccines are rolled out more broadly, the numbers of those skipping their second dose have gone up.  But the trend is nonetheless troubling some state officials, who are rushing to keep the numbers of only partly vaccinated people from swelling.  In Arkansas and Illinois, health officials have directed teams to call, text or send letters to people to remind them to get their second shots. In Pennsylvania, officials are trying to ensure that college students can get their second shots after they leave campus for the summer. South Carolina has allocated several thousand doses specifically for people who are overdue for their second shot.  Mounting evidence collected in trials and from real-world immunization campaigns points to the peril of people skipping their second doses. Compared with the two-dose regimen, a single shot triggers a weaker immune response and may leave recipients more susceptible to dangerous virus variants. And even though a single dose provides partial protection against Covid, it’s not clear how long that protection will last. “I’m very worried, because you need that second dose,” said Dr. Paul Offit, a professor at the University of Pennsylvania and a member of the Food and Drug Administration’s vaccine advisory panel. The stakes are high because there is only one vaccine authorized in the United States that is given as a single shot. The use of that vaccine, made by Johnson & Johnson, was paused this month after it was linked to a very rare but serious side effect involving blood clotting. Federal health officials on Friday recommended restarting use of the vaccine, but the combination of the safety scare and ongoing production problems is likely to make that vaccine a viable option for fewer people.

 

The C.D.C.’s count of missed second doses is through April 9. It covers only people who got a first Moderna dose by March 7 or a first Pfizer dose by March 14. While millions of people have missed their second shots, the overall rates of follow-through, with some 92 percent getting fully vaccinated, are strong by historical standards. Roughly three-quarters of adults come back for their second dose of the vaccine that protects against shingles. In some cases, problems with shipments or scheduling may be playing a role in people missing their second doses. Some vaccine providers have had to cancel appointments because they did not receive expected vaccine deliveries. People have also reported having their second-dose appointments canceled or showing up only to find out that there were no doses available of the brand they needed. Some people can be flexible about being rebooked. But that’s harder for people who lack access to reliable transportation or who have jobs with strictly scheduled hours, said Elena Cyrus, an infectious disease epidemiologist at the University of Central Florida. Walgreens booked some customers for their second appointments at places that didn’t have the same vaccine that they had received for their initial doses. The company said it fixed the problem in late March.  Susan Ruel, 67, was scheduled to get her two vaccine doses at different Walgreens stores in Manhattan. She said she got her first Pfizer dose without incident in February, but when she arrived for her second appointment, she was told that the store only had Moderna doses in stock. A Walgreens pharmacist told Ms. Ruel that there was another Walgreens pharmacy less than two miles away with Pfizer doses in stock. While Ms. Ruel was waiting for the subway to take her there, she got a phone call: That Walgreens store had run out of Pfizer doses, too....

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Second Dose of Pfizer-BioNTech COVID-19 Vaccine May Not Benefit Previously Infected Individuals

Second Dose of Pfizer-BioNTech COVID-19 Vaccine May Not Benefit Previously Infected Individuals | Virus World | Scoop.it

Researchers at the NYU Grossman School of Medicine have shown that a second dose of the Pfizer-BioNTech BNT162b2 vaccine may not offer any additional protection against coronavirus disease 2019 (COVID-19) over one dose among individuals previously infected with the causative agent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).  In a study evaluating immune responses to the Pfizer-BioNTech vaccine, Ramin Herati and colleagues observed robust humoral (antibody) responses following two vaccine doses among individuals without previous SARS-CoV-2 infection (SARS-CoV-2-naïve). However, SARS-CoV-2-experienced participants had a robust humoral response to the first dose but a muted response to the second dose. In fact, SARS-CoV-2-experienced individuals had lower circulating levels of antigen-specific antibody-secreting cells (ASCs) following the second dose than they did following the first dose. A pre-print version of the research paper is available on the medRxiv* server while the article undergoes peer review.

 

SARS-CoV-2 infection triggers important antibody responses

The SARS-COV-2 infection process is mediated by a surface structure called the spike protein, which binds to the host cell receptor angiotensin-converting enzyme 2 (ACE2) via its receptor-binding domain (RBD). The spike protein comprises two subunits. Subunit 1 (S1) contains the RBD, which attaches to ACE2 via a receptor-binding motif (RBM) and subunit 2 (S2) enables the viral membrane to fuse with the host cell. Following natural infection, antibodies targeting the spike RBD are thought to account for more than 90% of the neutralizing activity against SARS-CoV-2. Research has shown that pre-existing immunity to SARS-CoV-2 is associated with protection against reinfection in humans and animals.

Recently approved vaccines are based on the spike protein

Both the Pfizer-BioNTech and Moderna vaccines that have recently been FDA-approved for emergency use against SARS-CoV-2 are mRNA-based vaccines that encode a region of the spike protein. These novel mRNA vaccines have been considered critical to ending the COVID-19 pandemic since they were shown to induce robust humoral responses against SARS-CoV-2 and to be 94% effective at preventing disease in large-scale clinical trials. However, efficacy trials excluded individuals with a prior diagnosis of COVID-19 and only focused on individuals without previous SARS-CoV-2 exposure.

What did the researchers do?

The team evaluated immune responses among 32 individuals (aged 24 to 62 years) who received the Pfizer-BioNTech BNT162b2 vaccine as a two-dose regimen. Thirteen of the participants (median age 41 years) had previously been infected with SARS-CoV-2 and the remaining 19 (median age 39 years) were SARS-CoV-2-naïve. All participants had immune responses assessed at approximate intervals before and after each dose of the vaccine.

What did the study find?

Following the first vaccine dose, anti-S1 immunoglobulin G (IgG) titers increased 47-fold among the SARS-CoV-2-experienced individuals and 2.6-fold among the SARS-CoV-2-naïve participants. However, following the second dose, anti-S1 IgG titers only increased 1.4-fold among the SARS-CoV-2-experienced participants, whereas they increased 13-fold among SARS-CoV-2-naïve individuals. One week after the second dose, anti-S1 IgG titers were similar between the two groups. Similarly, while antigen-specific ASC responses increased following each vaccine dose among the SARS-CoV-2-naïve subjects, fewer circulating antigen-specific ASCs were detected among SARS-CoV-2-experienced participants after the second vaccine, compared with after the first dose. After the second dose, reductions in circulating antigen-specific ASCs were observed for S1, S2 and the RBD among SARS-CoV-2-experienced participants.

What are the implications of the study?

The researchers say the findings highlight the need to investigate further the impact that prior immunological experience of SARS-CoV-2 may have on responses to COVID-19 vaccines.

 

Preprint available (Feb. 9, 2021):

https://doi.org/10.1101/2021.02.07.21251311 

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