The delta variant of COVID-19 has swept the globe and is now confirmed in at least 130 countries. Even vaccinated people can now transmit the more infectious strain.
US health officials say new evidence shows that the variant is as contagious as chickenpox, and may be more dangerous than other versions.
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Officials around the globe have been taking steps to curb the spread of the delta variant. Japan expanded a state of emergency to four more areas, in addition to Tokyo, following record spikes in infections as it hosts the Summer Olympic Games. Cyprus plans to start the voluntary COVID-19 vaccination of children over the age of 12 next week, with Greece doing the same. Israeli health authorities began administering booster shots to people over 60 who've received both doses of a vaccine.
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And in the United States, President Joe Biden announced that federal workers will be required to sign forms attesting they’ve been vaccinated, or have to comply with new rules on mandatory masking, weekly testing, distancing and more.
To discuss the effects of the delta variant, Dr. Michael Marks, a researcher at the London School of Hygiene and Tropical Medicine, who also treats COVID-19 patients, spoke with The World's host Marco Werman.
Marco Werman: You've seen the delta surge in the UK. What is your reaction to this updated news from the US CDC, their analysis of transmission?
Dr. Michael Marks: So, I think what's becoming increasingly clear is that the vaccines remain very effective against delta, particularly for things like hospitalization, but are not quite as effective as they were for earlier strains of the virus. And so, your risk of becoming infected with delta, even if you're vaccinated, is higher than it was for the previous strains of the virus, and therefore, your risk of being infected and infectious to others is higher. Overall, the vaccines remain incredibly effective, particularly at preventing severe disease. But I can see how people are revisiting the need for thinking about your risk of spreading onto other people, even if you've been vaccinated — because this new strain is more infectious.
Are you seeing similar dynamics with delta transmission in other countries with similar vaccination rates to the US?
So, certainly, for example, in the UK, we've had a very large wave of cases that's occurred through June into July, despite having, relatively speaking, a very advanced vaccination program in terms of the coverage that we've achieved. But what's been really noticeable is that the rate of hospitalization has been significantly lower for the same number of cases than it has been in either the two previous waves. So, what that is showing us, again, these vaccines remain very effective, even with delta, against protecting us for the most severe outcomes, even if they're not quite as effective as they were earlier variants for protecting us.
Dr. Marks, throughout this pandemic in the US, we've been told one thing about transmission, about vaccines, about masking and socializing. And then the advice shifts again. What makes it hard to draw lasting conclusions about this virus and transmission?
So, I think there are a number of factors at play here. Firstly, the virus is mutating, or evolving, over time. We've seen the emergence from the original strain — alpha, beta, delta — different strains. And they respond differently, both to the vaccine in terms of the effectiveness of the vaccine, and to their inherent transmissibility. And that means it's difficult to make a prediction now and not know that a new variant won't emerge in three or six months time, which responds differently to the vaccine. Secondly, we were making predictions based on the original trials of the vaccine, and the original trials of the vaccine were all very focused on preventing symptomatic illness. And what's happening as those vaccines are rolled out on a larger scale, is every week, every month, we are understanding more about impact, not only on symptomatic illness, but on your risk of becoming infected at all, or your risk of transmitting. Those things are constantly evolving and moving.
So, how do you recommend people approach decision-making and risk assessment right now?
So, I think that's a challenging situation to give sort of personalized guidance for, but I think people need to bear in mind a number of facts. The vaccines are effective, but they're not completely effective. So, just because you are vaccinated, or the people you're mixing with are vaccinated, does not take away all of the risk. And all of the things that we've always known, as WHO is highlighting, [that] are associated with risk, continue to be so. So, prolonged contact with people, closer contact with people, contact with large numbers of individuals, those all remain circumstances which favor the transmission of COVID-19. So, meeting outside, meeting small groups, meeting at a distance, use of masks, these all remain things that we can predict to be of value, regardless of which strain of the virus we're talking about, and regardless of people's vaccination status. Now, that will change over time. As everyone becomes vaccinated, the space for the virus to transmit will go down. And one of the challenges we see is the lack of equity in access to vaccines. So, for example, huge discrepancies in the proportion of populations that have been vaccinated in America, Europe, the UK, compared to low- and middle-income settings, where that means viruses will continue to be transmitted, putting us all at risk. So, if we really want to address the fundamental problems, we're going to have to improve vaccine coverage and equity everywhere.
This interview has been lightly edited and condensed for clarity. AP contributed to this report.