Coronavirus Research Tracking - 30 April
Indian resurgence, real world vaccine effectiveness, wearing masks outside, anti-vaccination responses
This Research Tracker focuses mainly on studies demonstrating the effect the Pfizer/BioNTech, Moderna, and AstraZeneca/Oxford vaccines have on infection risks, symptoms, immune responses, or side effects. Many of these papers come from large scale studies in the UK.
The Research Tracker is prepared by Dr Robert Hickson for the Science Media Centre.
What’s behind the Indian resurgence?
A news item in Nature discusses why the resurgence in India is surprising. The early wave of infection was thought to have resulted in more than 50% in the large cities becoming infected (and perhaps 20% of India’s population), so a strong resurgence was thought to be unlikely. Several factors are likely to be involved, including biases in earlier infection estimates, few restrictions on social interactions, low levels of vaccination, and possibly more infectious variants.
Good T cell responses induced by the mRNA vaccines
The two mRNA vaccines induce good T cell responses, similar to those generated by natural infections. This includes the production of long lasting memory cells. Vaccination also resulted in coordinated T cell and humoral immune responses. These are good indicators that durable immunity is generated by the Pfizer/BioNTech and Moderna vaccines.
The study also found that, similar to humoral responses, if those being vaccinated had been previously infected then the second vaccine shot did not have much effect on T cell responses. The paper has not yet been peer reviewed.
A paper submitted to The Lancet, but not yet peer reviewed, also found that T cell (and antibody) responses to the Pfizer/BioNTech vaccine were stronger in previously infected people after the first dose. Both doses were required in uninfected people to show a similar level of response.
Those who had been previously infected and then vaccinated also demonstrated a stronger neutralisation ability against the B.1.351 variant than uninfected vaccinated people.
Pfizer/BioNTech and AstraZeneca/Oxford vaccines reduce infection risk
Single doses of the AstraZeneca/Oxford or the Pfizer/BioNTech vaccine significantly reduced infections in the UK. The odds of an infection decreased by 65% overall when assessed at least three weeks after vaccination. Two doses of the Pfizer vaccine had the greatest impact on reducing reported symptoms and viral loads. This is based on a study of 373,000 participants, mostly of white ethnicity and with a median age of 55. The greatest reduction in infections was seen in those over 75. The study has not yet been peer reviewed.
Another study showed that the Pfizer/BioNTech vaccine is effective against the B.1.1.7 variant in those over 80. A large matched UK study compared infection rates in over 170,000 vaccinated 80 to 83 year olds with matched unvaccinated 76 to 79 year olds. Five to seven weeks after the first vaccination (when nearly 80% had received their second dose), emergency hospitalisations were 75% lower and infections 70% lower, compared to the unvaccinated group. The study has not yet been peer reviewed.
Pfizer/BioNTech and Moderna vaccines can also reduce likelihood of symptomatic infection
Another large UK study, involving 23,000 healthcare workers, found that a single dose of the Pfizer/BioNTech vaccine showed vaccine effectiveness of 70% after three weeks, and 85% one week after the second dose. Those who were vaccinated but became infected were less likely to display Covid-19 symptoms. A study limitation was that most participants were female and of white ethnicity, with a median age of 46 years. The study was published in The Lancet Microbe.
A similar outcome was seen in an outbreak in a US nursing facility. Both vaccinated (with the Pfizer/BioNTech vaccine) and unvaccinated residents and staff became infected. However, unvaccinated residents and staff were three to four times more likely to be infected. It was calculated that the vaccine was 86.5% protective for residents, and 87.1% for staff. Six of the eight unvaccinated residents become infected, compared to only 18 of 71 fully vaccinated residents. Four of 56 vaccinated health care professionals became infected, compared to 16 of 54 who were unvaccinated.
Those vaccinated and infected were significantly less likely to develop symptoms or require hospital attention. The paper was published in the Morbidity and Mortality Weekly Report.
A multi-state study involving 400 patients in the US found that the Pfizer/BioNTech and Moderna vaccines substantially reduce the risk of hospitalisation in those 65 years and older. Having both vaccine doses reduced the risk of hospitalisation due to Covid-19 by 94%, while the effectiveness was 64% if people had received only the first dose or they became infected less than two weeks after the second dose.
The study has a relatively small sample size, but the results are consistent with several other studies demonstrating high levels of protection. The paper was published in the Morbidity and Mortality Weekly Report.
In a study of over 90,000 people with Covid-19 in the US, vaccinations significantly reduced hospitalisations and deaths. In those who were fully vaccinated (with either mRNA vaccine) only 0.7% were hospitalised due to Covid-19, compared with 3.4% of partially vaccinated people, and 2.7% of unvaccinated individuals.
The overwhelming majority (97.3%) of Covid-19-related deaths were in unvaccinated people, compared with only 0.0041% in fully vaccinated people. The paper has not yet been peer reviewed.
Immune responses boosted when vaccines given to previously infected people
Further evidence confirms that a stronger immune response occurs after a single vaccine dose in people who have previously been infected. The UK study, involving nearly 46,000 people, compared responses to the AstraZeneca/Oxford and the Pfizer/BioNTech vaccines.
It found that in previously uninfected people, a single vaccine dose resulted in lower antibody levels in people over 60, compared with younger age groups. Stronger antibody responses across all ages were found after two doses, and in those who were previously infected and had a single vaccination.
For those receiving the AstraZeneca vaccine, antibody levels rose more slowly and to lower levels than seen in those who received the first Pfizer dose. However, antibody levels in AstraZeneca vaccines then remained stable, while levels in those who had one Pfizer dose declined.
About 6% of those vaccinated showed poor antibody responses. The study has not yet been peer reviewed.
Moderate and short-lived side effects seen for Pfizer/BioNTech and AstraZeneca/Oxford vaccines
A large UK study of over 600,000 vaccinated people found that short-term side effects from the Pfizer/BioNTech and AstraZeneca/Oxford vaccines are moderate in frequency, mild in severity, and short-lived. The side effects were not as common as observed in the Phase 3 clinical trials, despite the vaccinees being on average much older than those in the trials.
More than half of vaccinated people reported local side effects after vaccinations, while systemic side effects were reported by 13.5% and 22% after the first and second doses of the Pfizer vaccine, and by 33.7% who received the AstraZeneca vaccine.
The study also found that side effects were more common in people who had previously been infected by SARS-CoV-2.
Risk of infection was reduced by 60% (AstraZeneca) or 69% (Pfizer) three to six weeks after vaccination. By eight weeks the Pfizer/BioNTech vaccine had reduced infection risk by 72%. The infection risk reduction was lower for those over 55 and those with comorbidities. The paper was published in The Lancet Infectious Diseases.
Model indicates more deaths likely to occur by delaying use of AstraZeneca/Oxford than would die from rare thrombosis
A modelling study in France showed that delaying AstraZeneca/Oxford vaccinations results in substantially more deaths than those attributed to thrombosis as a possible side effect of the vaccine. This increase in deaths is seen even if vaccination is halted only for a few days. The model does not consider other vaccines replacing AstraZeneca’s. The paper was published in the journal Chaos.
US scientist concerned that official responses to anti-vaccination activities are inadequate
An opinion piece in Nature by a vaccine researcher suggests that health agencies underestimate or deny the reach of anti-science forces, and are ill-equipped to counteract their activities. It notes that globally there are hundreds of anti-vaccine websites and more than 50 million followers on social media. Some of the groups are using anti-vaccination as part of a broader political agenda. While accurate and targeted counter-messaging is necessary, the writer suggests that it is insufficient. He suggests that more direct approaches are necessary to counter disinformation on vaccines being produced by Russian groups and extremist groups in the US.
Asymptomatic infections generate good immune responses
Asymptomatic infections generate antibody and neutralisation responses. The levels of antibodies and their functions (ability to neutralise and kill the virus) were lower in asymptomatic cases, supporting previous research which showed that disease severity correlates with the level of antibody functions. The study compared the antibody responses of 52 asymptomatic individuals, with those in 119 people with mild symptoms and 21 who were hospitalised with Covid-19. The paper was published in Cell Reports Medicine.
Rapid antigen tests are useful at the start of an outbreak
Rapid antigen tests can be useful in identifying early stage infections and people shedding the virus. The study, carried out at a US nursing home found that the antigen test they used was less accurate, when compared with PCR results, later in the infection. The researchers recommend using rapid antigen tests early and frequently during an outbreak to identify infectious people, although costs of antigen tests can be high. The study was published in Annals of Internal Medicine.
A debate about wearing masks outside
Reasons for and against wearing masks outside are presented in an article in the British Medical Journal. While there is agreement that most transmission events occur indoors, those recommending outdoor mask wearing suggests that it helps normalise mask wearing so that more people will wear masks indoors. They also note that it will help reduce transmission risks at large outdoor events where there is little social distancing.
Those arguing against mandating outdoor mask wearing highlight the low risk of transmission outside, and suggest that requiring outdoor mask use could be seen as arbitrary and undermine public confidence in health measures and requirements. It can also confuse people about relative risks, and result in more people staying or gathering indoors where risks are greater.
Long Covid Q&A
A NZ Science Media Centre Expert Q&A provides context and answers from two New Zealand researchers about Long Covid.
Complex interactions between the virus and the cell
At least 109 host molecules bind to SARS-CoV-2 RNA. Some of these help the virus replicate, while others inhibit it. The study, which was published in Molecular Cell, highlights the complexity of interactions following infection, as well as identifying potential new therapies.