Transmission

Vaccinated “No Less Infectious” Than Unvaccinated, CDC Study Finds

A pre-print study out this week from the U.S. Government’s Covid Response Team at the Centers for Disease Control and Prevention (CDC) has found vaccinated people to be “no less infectious” than unvaccinated people.

The study tested inmates in a federal prison with high vaccination rates daily during a SARS-CoV-2 Delta variant outbreak.

The study was very thorough. Inmates who tested positive for SARS-CoV-2 were, where willing, PCR-tested for 10 consecutive days and reported symptoms via a questionnaire. The researchers performed whole genome sequencing and viral culture analysis on a high proportion of the 978 specimens collected, allowing them to assess the duration of PCR positivity and viral culture positivity.

There were 95 participants in total, of whom 78 (82%) were double vaccinated and 17 (18%) were not double vaccinated (two having received one dose and 15 having received none). No significant differences were found between double vaccinated and not double vaccinated either in duration of PCR positivity (13 days each) or in duration of culture positivity (five days each).

The authors conclude that “clinicians and public health practitioners should consider vaccinated persons who become infected with SARS-CoV-2 to be no less infectious than unvaccinated persons”.

This is in line with the findings of Public Health England and others.

While this sounds like more good news for countering vaccine passports, vaccine mandates and all other vaccine-based coercion and discrimination, it may be less good news for ending general restrictions and interventions. The authors state: “These findings are critically important, especially in congregate settings where viral transmission can lead to large outbreaks.” Which suggests they think the lack of efficacy against transmission is a reason to intervene more generally to prevent “large outbreaks” in “congregate settings”. It could be a long winter.

Vaccination Has No Impact on Household Transmission of the Delta Variant, Study Finds

According to a recent study published in the Lancet, those who have received a Covid vaccine are just as likely as the unvaccinated to transmit the Delta variant within a household setting. In addition, researchers uncovered that both the unvaccinated and the vaccinated had a similar viral load of the disease when infected, with 25% of vaccinated household contacts contracting the disease. The Hill has the story.

According to the study published in the Lancet Infectious Diseases journal, people who contracted Covid had a similar viral load regardless of whether they had been vaccinated. The study further found that 25% of vaccinated household contacts contracted Covid while 38% of unvaccinated individuals were diagnosed with the disease.

Researchers examined 621 symptomatic participants in the United Kingdom over a year.

“Although vaccines remain highly effective at preventing severe disease and deaths from Covid, our findings suggest that vaccination is not sufficient to prevent transmission of the Delta variant in household settings with prolonged exposures”, the study said.

In contrast, researchers noted that the vaccination was more effective at curbing transmission of the Alpha variant within the household, at between 40 and 50%. 

“Increasing population immunity via booster programmes and vaccination of teenagers will help to increase the currently limited effect of vaccination on transmission, but our analysis suggests that direct protection of individuals at risk of severe outcomes, via vaccination and non-pharmacological interventions, will remain central to containing the burden of disease caused by the Delta variant”, the researchers wrote.

Worth reading in full.

Devastating New Data From PHE Shows Vaccine Effectiveness Down to 17% and No Reduction in Infectiousness – But Mortality Cut by 77%

Public Health England yesterday released their latest technical briefing on the variants of concern, number 20, and it has some illuminating data.

It provides us with the infection, hospitalisation and death rates for the Delta variant, broken down by vaccination status and age. This allows us to do a calculation of the real-world vaccine effectiveness in the over-50s during the Delta surge, albeit a rough one without any adjustments.

The latest report has data up to August 2nd. If we substract from these values the data in Briefing 17 (up to June 21st) then we get the data covering the period June 22nd to August 2nd, which broadly corresponds to the bulk of the Delta surge in the U.K. The vaccine rollout to the over-50s was basically complete by this point, having stabilised according to PHE at around 88% double vaccinated and 10% unvaccinated (the other two per cent remaining single vaccinated, perhaps due to a bad reaction to the first dose).

In this period the PHE data tells us there were 2,464 Delta cases in the unvaccinated over-50s and 17,926 in the fully vaccinated over-50s. From this we can estimate the vaccine effectiveness against infection in the over-50s during the Delta surge as 17% (1-[(17,926/88%)/(2,464/10%)]). This confirms using additional data the estimate I made last week.

We can make a similarly rough calculation of the vaccine effectiveness against death. Between June 22nd and August 2nd, PHE reports that among the over-50s there were 339 deaths with the Delta variant in the double vaccinated and 167 in the unvaccinated. Using the same proportions vaccinated and unvaccinated as above, this gives a vaccine effectiveness against death in the over-50s during the Delta surge of 77% (1-[(339/88%)/(167/10%)]). Interestingly, this is very similar to the latest estimate of vaccine effectiveness against serious disease from Israel, which is around 80%. This is a decent level of protection and helps explain why the Delta surge had proportionally fewer hospitalisations and deaths, but it is well below the levels suggested by earlier studies and quoted by PHE, which are north of 95%.

The Outbreak Point: Are Covid Outbreaks Triggered When the Viral Load in the Air Hits a Certain Threshold?

In recent posts I’ve been exploring the question of why COVID-19 (much like other seasonal viruses) has a Jekyll and Hyde-like nature, being puny for much of the year then exploding in short, sharp outbreaks for a few weeks at a time, usually though not exclusively in the winter. I argued in a post last week that seasonality appears to be driven largely by cycles in the human immune system (though there may be environmental factors such as UV radiation, temperature and humidity as well). The trigger for the somewhat irregular (and not necessarily winter) outbreaks appears to be the appearance of a new variant (or virus) that is able to infect slightly more people, amounting to just one in 18 additional people when estimated from the secondary attack rate. The end of the outbreaks then corresponds to the exhaustion of the small pool of newly susceptible people and the restoration of the temporarily disturbed herd immunity.

I noted that the difference between a surge and a decline amounted only to a small absolute change in the R growth rate, from 1.3 during a surge to 0.8 during a decline, and that the shift between these rates often occurs very abruptly. This means that infected people quite suddenly start infecting 1.3 other people before, around three and a half weeks later, just as suddenly switching back to infecting just 0.8 people. This change in R is reflected in a similar change in the secondary attack rate (the proportion of contacts an infected person infects), which varies between around 15% during surges to around 10% outside of them. I observed that this difference is small enough to be explained by a slightly increased susceptibility to a new variant and a subsequent restoration of herd immunity a short time later.

After writing this it occurred to me that with such a subtle trigger it would seem that outbreaks should be highly sensitive to the amount of social contact people have with one another, and thus to the imposing and lifting of restrictions (or to voluntary social distancing). Indeed, it is logic like this which presumably explains why SAGE members and other scientists persist in believing in the efficacy of lockdowns regardless of how much data emerges showing they don’t make any significant impact on the infection or death rate.

A recent set of SAGE minutes explains the logic of restrictions:

As Evidence Grows That Vaccines Do Not Protect Against Infection, the Case For Granting Privileges to the Vaccinated Collapses

Creating a two-tier society where freedoms and opportunities are contingent on whether or not you have received a novel (and not fully tested or licensed) vaccine, and having to reveal that fact to strangers, was never a sound approach from a civil liberties point of view. But as the evidence grows that the vaccines do not prevent infection or transmission, the medical case against this new medical apartheid falls apart as well.

The Covid vaccines were originally intended to protect the vulnerable from serious disease and death, following which life could then return to normal. At some point, though, a new idea emerged: that everyone (including children) should be vaccinated, not in order to protect themselves (their risk was low) but to provide further protection to the vulnerable. Similarly, the idea appeared that the fully vaccinated should have freedoms that the unvaccinated did not, because they were no longer able to transmit the virus.

It’s becoming increasingly clear that this idea is incorrect, and the vaccines do not meaningfully prevent infection or transmission, particularly from new variants. Yesterday, Lockdown Sceptics reported on the new data from Israel showing that the effectiveness of the Pfizer vaccine against infection had dropped to 64% during the current Covid surge, down from 94% the previous month. (Effectiveness against serious disease as a result of becoming infected held up much better at 93%.) Public Health England has already reported that the effectiveness of the AstraZeneca vaccine has dropped to 60% against the Delta variant. Even these new lower figures may be overestimates, since Israel reports that 55% of new cases are in fully vaccinated people, and since 60% of the country is fully vaccinated this suggests the vaccines are doing very little to prevent infection (a vaccine efficacy estimate on those raw figures would give just 18.5%).

There have also been major outbreaks in highly vaccinated countries like Bahrain, Seychelles, Maldives and Chile.

Underlining the point, the Swiss Doctor has highlighted a case where “a vaccinated Israeli caught the Indian variant in London, infected another vaccinated person in Israel, who infected another vaccinated person, who infected about 80 students at a high school party”.

To some, the idea that the vaccines do not prevent infection or transmission comes as no surprise. As Peter Doshi wrote in the BMJ in October, the trials were not designed to establish this. Furthermore, the vaccines do not produce mucosal IgA antibodies, which have been shown to play a crucial role in fighting infection in the early stages.

Time for governments to abandon the idea that vaccination provides meaningful protection against infection or transmission, and thus any idea of vaccinating people to protect others, or conferring privileges on the vaccinated, including for international travel, as though they will no longer spread the virus.

Governments should make clear that vaccination is purely for personal protection, and therefore also a personal choice in regard to personal risk. There is no social obligation to get vaccinated to protect others, no benefit to vaccinating children, and no warrant for restricting the freedoms and opportunities of the unvaccinated or imposing on them extra costs such as quarantine.

Transmission of COVID-19 Is Influenced by Temperature, Humidity and UV Radiation, Study Finds

The issue of COVID-19’s seasonality has been covered extensively on Lockdown Sceptics. Back in February, Glen Bishop noted that a model developed by Imperial College researchers – which predicted there would be an additional 130,000 deaths this summer – assumed that transmission does not vary by season.

In a follow-up article, I reviewed eight separate studies that found evidence for the seasonality of COVID-19. Indeed, it would be rather surprising if COVID-19 wasn’t seasonal given what we know about other human coronaviruses, i.e., that they are – in the words of one recent study – “sharply seasonal”. 

However, doubts have been expressed about whether COVID-19 is in fact a seasonal disease. Such doubts are based on the observation that countries like Chile and South Africa saw epidemics burgeon during their summer months, and that Britain itself is now seeing a rise in cases.

But as the biologist Francois Balloux notes in a recent Twitter thread, the fact that some countries have seen infections rise during the summer is not inconsistent with seasonal factors playing a role in transmission. It just means they aren’t the only factors involved. (One also has to consider viral evolution, population immunity and human behaviour.)

A new study by researchers from Yale and Columbia (which was published in the journal Nature Communications) offers particularly strong evidence for the seasonality of COVID-19. The authors looked at the relationship between seasonal factors and the R number across US counties between March and December of last year.

They ran a statistical model of the R number, with temperature, specific humidity and UV radiation as predictors. The model controlled for a range of other factors, including spatial, demographic and socio-economic variables.

The authors found that each of the three seasonal factors was independently associated with R. They then calculated the fraction of R that was attributable to seasonality, and obtained a value of 17.5%. Interestingly, specific humidity was the most important of the three, contributing 9.4%. 

The authors’ findings indicate that “that cold and dry weather and low levels of UV radiation are moderately associated with increased SARS-CoV-2 transmissibility”. However, they were unable to examine possible differences in seasonality across different variants, leaving this as a topic for future research.

Overall, their study provides some of the best evidence yet for seasonality. And it gives one more reason to be sceptical that the current rise in cases here in Britain portends a major epidemic. 

Government Told to Ban Perspex Screens in Pubs and Offices Because They Increase Transmission

Perspex screens appear to have joined the long list of measures introduced to mitigate the impact of SARS-CoV-2 which actually make matters worse. Alex Wickham of Politico has got hold of a leaked planning document describing what Stage 4 of the roadmap will look like and what social distancing measures will remain in place throughout the winter and possibly beyond. He reports that the Government has been urged to ban the use of these screens in pubs, restaurants and offices.

Not only do Perspex screens not stop the spread of the virus, they may actually increase transmission! More from Alex here:

Problems include them not being positioned correctly, with the possibility that they actually increase the risk of transmission by blocking airflow. Therefore there is clear guidance to ministers that these perspex screens should be scrapped.

Even if perspex screens are scrapped, the guidelines on face masks will likely remain place in some settings “long-term”, Alex Reports, despite evidence of their benefits being equally threadbare.

Stop Press: You can read more about the leaked Stage 4 planning document here.

Claims the Indian Variant is “Hyper-Transmissible” are Nonsense – And Here’s the Graph that Proves It

Yesterday I wrote about the latest Public Health England (PHE) report claiming that the Delta (Indian) variant is much more infectious than the Alpha (British) variant. I noted that the main measure of transmissibility – the secondary attack rate (i.e., the proportion of contacts that an infected person infects) – has varied over time.

It occurred to me that it would be useful to plot these attack rate values to show them graphically. So I went through the 15 technical briefings released by PHE so far and extracted the secondary attack data for the three variants (Wuhan, Alpha, Delta) and plotted them in the graph above.

There are a few points worth making from this about the infectiousness of the Covid variants.

First, between 85% and 92% of the contacts of all those infected with any of the COVID-19 variants do not get infected. This is an indication of the high level of immunity (i.e., low level of susceptibility) in the population and the low absolute infectiousness of the virus.

Second, new variants appear to start off with – or quickly acquire – a high attack rate compared to established variants, a rate which then declines. The decline for the Alpha variant occurred prior to any significant vaccine coverage meaning it cannot all be attributed to the vaccines. Conversely, despite the high vaccine coverage in April and May the Delta attack rate spiked. Nonetheless, it has already sharply declined. (The reason for the sudden drop in the Alpha attack rate from 10% to 8% at the end of April is unclear.)

Third, the Alpha variant was once more transmissible than the Delta variant at its recent peak, but is now much less transmissible.

While more data from more variants would help to confirm the patterns here, the data so far suggest that new variants will often be more infectious than established variants to begin with, but this will not last. Further, the degree of infectiousness appears to arise more from factors such as the epidemic phase or the season than inherent properties of the variant, save insofar as the new variant is slightly better at evading our immune defences for a time. And I mean slightly. Only 3% more contacts of those infected with the Delta variant are being infected compared to the Alpha variant, a difference that is dropping week on week.

The upshot is we should stop being frightened by claims that the latest new variant is “50% more infectious”, which are a distraction, and focus on levels of serious disease and how best to cope with them.

PHE Briefing Claims Indian Variant is 64% More Infectious – But Dig Down and the Finding Falls Apart

Public Health England (PHE) released its latest technical briefing (number 15) yesterday on “variants of concern” which claimed the Delta (Indian) variant is 64% more infectious than the Alpha (British) variant. But look closer and you find this headline finding is not all it seems.

In the underlying study the researchers admit they did not control for the crucial factor of household size – bigger households will tend to have more secondary infections because there are more people in the household being exposed. The authors acknowledge that many of the Delta variant households may have been larger than Alpha variant households (say, because of different proportions of different ethnic groups), and also that many of the matched controls may have lived alone – they have no way of knowing.

We did not have information on household size, which is likely to have an effect on the estimates of transmissibility. For example, some controls (sporadic cases) will have lived alone and have no chance of onward transmission within their residence and therefore becoming a household cluster. However, we were unable to identify and exclude these cases in the analysis. Further studies of household transmission that includes denominators of all individuals in the household and their vaccination status are needed to provide improved estimates of household transmission and allow for the calculation of household secondary attack rates.

This factor by itself undermines the entire 64% claim and means it should be ignored.

Separate to this, the technical briefing provides some raw data on secondary attack rates (the proportion of contacts infected people infect) that give us an important insight into the real transmissibility of the variants.

Lack of Attention to Airborne Transmission Led to Blunders in Pandemic Management

In the early weeks of the pandemic, we were inundated with reminders to “wash our hands”. It was said that 20 or even 30 seconds of thorough scrubbing was needed to kill any particles that might be lurking there. 

And we were treated to some rather patronising instructional videos. You’d assume that most adults were already familiar with the concept of hand-washing. (Telling us to “be thorough” would probably have sufficed). 

Yet more and more evidence emerged that surfaces (known in the medical jargon as “fomites”) are not an important mode of transmission for SARS-CoV-2. Which is not to say you shouldn’t wash your hands.

However, there was still a dispute over whether respiratory droplets or airborne particles play a greater role in viral spread. Droplets are transmitted over short distances, and fall to the ground quickly. (Hence the ‘2m rule’.) Airborne particles, on the other hand, can remain aloft for minutes or even hours, and travel much greater distances. 

Over the last couple of months, it’s become clear that COVID is primarily transmitted via airborne particles. (Though some would say this was clear as early as the Diamond Princess outbreak, when several hundred passengers caught the virus on a cruise ship.)

In a recent article for the New York Times, the science writer Zeynep Tufekci reviews the debate over the transmission of SARS-CoV-2 and explains how mistaken assumptions led to errors in pandemic management. 

She begins by noting it was only on April 30th this year that the WHO finally updated its website to indicate that COVID is transmitted via both droplets and airborne particles. Until then, it simply had claimed, “the main way the virus spreads is by respiratory droplets”.

As Tufekci notes, this mistaken assumption led to errors of both commission (like closing playgrounds) and omission (like ignoring ventilation).

If the importance of aerosol transmission had been accepted early, we would have been told from the beginning that it was much safer outdoors, where these small particles disperse more easily, as long as you avoid close, prolonged contact with others. We would have tried to make sure indoor spaces were well ventilated, with air filtered as necessary. 

This also implies that plastic shields – which you might have seen in your local gym or supermarket – do essentially nothing to prevent transmission:

There was no attention to ventilation, installing air filters as necessary or even opening windows when possible, more to having people just distancing three or six feet, sometimes not requiring masks beyond that distance, or spending money on hard plastic barriers, which may be useless at best. (Just this week, President Biden visited a school where students were sitting behind plastic shields.)

Indeed, one of the safest places to be during the pandemic is outdoors. (As I’ve noted before, the vast majority of infections occur in indoor spaces.) This raises serious questions about the Government’s stay-at-home order, which confined us to our homes for weeks, with only one form of outdoor exercise per day. 

Particularly absurd was when police forces used drone footage to shame people who were out walking in the countryside (most likely from indoor offices where the risk of transmission was far higher.)

If COVID mainly spreads via airborne particles, then telling people not to go outside doesn’t really make sense. And in fact, a study published in Proceedings of the National Academy of Sciences examined shelter-in-place orders in the United States, but did “not find detectable effects of these policies on disease spread or deaths.”

Tufekci compares the lack of attention to airborne transmission of COVID with our misunderstanding of cholera’s spread in the era before John Snow:

So much of what we have done throughout the pandemic — the excessive hygiene theater and the failure to integrate ventilation and filters into our basic advice — has greatly hampered our response. Some of it, like the way we underused or even shut down outdoor space, isn’t that different from the 19th-century Londoners who flushed the source of their foul air into the Thames and made the cholera epidemic worse.

Tufekci’s article contains a lot of interesting details, and is worth reading in full.