Virus World

A Fourth Dose of mRNA Vaccine in Health Care Workers Health care workers in Israel were given a fourth dose of BNT162b2 or mRNA-1273 vaccine during a period of omicron-variant predominance. Level. In this open-label, nonrandomized clinical study, we assessed the immunogenicity and safety of a fourth dose of either BNT162b2 (Pfizer–BioNTech) or mRNA-1273 (Moderna) administered 4 months after the third dose in a series of three BNT162b2 doses (ClinicalTrials.gov numbers, NCT05231005. opens in new tab and NCT05230953. opens in new tab; the protocol is available with the full text of this letter at NEJM.org). Of the 1050 eligible health care workers enrolled in the Sheba HCW COVID-19 Cohort, 154 received the fourth dose of BNT162b2 and, 1 week later, 120 received mRNA-1273. For each participant, two age-matched controls were selected from the remaining eligible participants (Fig. S1 in the Supplementary Appendix, available at NEJM.org). 

After the fourth dose, both messenger RNA (mRNA) vaccines induced IgG antibodies against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor-binding domain and increased neutralizing antibody titers (Fig. S3); each measure was increased by a factor of 9 to 10, to titers that were slightly higher than those achieved after the third dose, with no significant difference between the two vaccines. Concurrently, antibody levels in the control group continued to wane (Table S5). Both vaccines induced an increase in live neutralization of the B.1.1.529 (omicron) variant and other viral strains by a factor of approximately 10 , similar to the response after the third dose. We found that the fourth dose did not lead to substantial adverse events despite triggering mild systemic and local symptoms in the majority of recipients (Fig. S2 and Table S4A and S4B).  Because of the extremely high infection incidence and meticulous active surveillance with weekly SARS-CoV-2 polymerase-chain-reaction testing, we were also able to assess vaccine efficacy with a Poisson regression model (see the Supplementary Appendix). Overall, 25.0% of the participants in the control group were infected with the omicron variant, as compared with 18.3% of the participants in the BNT162b2 group and 20.7% of those in the mRNA-1273 group. Vaccine efficacy against any SARS-CoV-2 infection was 30% (95% confidence interval [CI], −9 to 55) for BNT162b2 and 11% (95% CI, −43 to 44) for mRNA-1273. Most infected health care workers reported negligible symptoms, both in the control group and the intervention groups. However, most of the infected participants were potentially infectious, with relatively high viral loads (nucleocapsid gene cycle threshold, ≤25) (Table S6). Vaccine efficacy was estimated to be higher for the prevention of symptomatic disease (43% for BNT162b2 and 31% for mRNA-1273) (Fig. S4).

Limitations of the study include its nonrandomized design and the 1-week difference between enrollment in the two intervention groups, generating potential biases. To overcome this, we assessed each intervention group separately and used a Poisson model accounting for calendar time. In addition, despite similar requests for weekly SARS-CoV-2 testing, adherence was slightly lower in the control group. We did not sequence the infecting virus and cannot be absolutely certain that all cases were caused by the omicron variant; however, during the study period, omicron accounted for 100% of the isolates that were typed. Finally, our cohort was too small to allow for accurate determination of vaccine efficacy. However, within the wide confidence intervals of our estimates, vaccine efficacy against symptomatic disease was 65% at most. Our data provide evidence that a fourth dose of mRNA vaccine is immunogenic, safe, and somewhat efficacious (primarily against symptomatic disease). A comparison of the initial response to the fourth dose with the peak response to a third dose did not show substantial differences in humoral response or in levels of omicron-specific neutralizing antibodies. Along with previous data showing the superiority of a third dose to a second dose, our results suggest that maximal immunogenicity of mRNA vaccines is achieved after three doses and that antibody levels can be restored by a fourth dose. Furthermore, we observed low vaccine efficacy against infections in health care workers, as well as relatively high viral loads suggesting that those who were infected were infectious. Thus, a fourth vaccination of healthy young health care workers may have only marginal benefits. Older and vulnerable populations were not assessed.

Published in NEJM (March 16, 2022):

https://doi.org/10.1056/NEJMc2202542

BACKGROUND

The emergence of the B.1.617.2 (delta) variant of severe acute respiratory syndrome coronavirus 2 and the reduced effectiveness over time of the BNT162b2 vaccine (Pfizer–BioNTech) led to a resurgence of coronavirus disease 2019 (Covid-19) cases in populations that had been vaccinated early. On July 30, 2021, the Israeli Ministry of Health approved the use of a third dose of BNT162b2 (booster) to cope with this resurgence. Evidence regarding the effectiveness of the booster in lowering mortality due to Covid-19 is still needed.

METHODS

We obtained data for all members of Clalit Health Services who were 50 years of age or older at the start of the study and had received two doses of BNT162b2 at least 5 months earlier. The mortality due to Covid-19 among participants who received the booster during the study period (booster group) was compared with that among participants who did not receive the booster (nonbooster group). A Cox proportional-hazards regression model with time-dependent covariates was used to estimate the association of booster status with death due to Covid-19, with adjustment for sociodemographic factors and coexisting conditions.

RESULTS

A total of 843,208 participants met the eligibility criteria, of whom 758,118 (90%) received the booster during the 54-day study period. Death due to Covid-19 occurred in 65 participants in the booster group (0.16 per 100,000 persons per day) and in 137 participants in the nonbooster group (2.98 per 100,000 persons per day). The adjusted hazard ratio for death due to Covid-19 in the booster group, as compared with the nonbooster group, was 0.10 (95% confidence interval, 0.07 to 0.14; P<0.001).

CONCLUSIONS

Participants who received a booster at least 5 months after a second dose of BNT162b2 had 90% lower mortality due to Covid-19 than participants who did not receive a booster.

Published in NEJM (Dec. 8, 2021):

https://doi.org/10.1056/NEJMoa2115624  

BACKGROUND

Despite high vaccine coverage and effectiveness, the incidence of symptomatic infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been increasing in Israel. Whether the increasing incidence of infection is due to waning immunity after the receipt of two doses of the BNT162b2 vaccine is unclear.

METHODS

We conducted a 6-month longitudinal prospective study involving vaccinated health care workers who were tested monthly for the presence of anti-spike IgG and neutralizing antibodies. Linear mixed models were used to assess the dynamics of antibody levels and to determine predictors of antibody levels at 6 months.

RESULTS

The study included 4868 participants, with 3808 being included in the linear mixed-model analyses. The level of IgG antibodies decreased at a consistent rate, whereas the neutralizing antibody level decreased rapidly for the first 3 months with a relatively slow decrease thereafter. Although IgG antibody levels were highly correlated with neutralizing antibody titers (Spearman’s rank correlation between 0.68 and 0.75), the regression relationship between the IgG and neutralizing antibody levels depended on the time since receipt of the second vaccine dose. Six months after receipt of the second dose, neutralizing antibody titers were substantially lower among men than among women (ratio of means, 0.64; 95% confidence interval [CI], 0.55 to 0.75), lower among persons 65 years of age or older than among those 18 to less than 45 years of age (ratio of means, 0.58; 95% CI, 0.48 to 0.70), and lower among participants with immunosuppression than among those without immunosuppression (ratio of means, 0.30; 95% CI, 0.20 to 0.46).

CONCLUSIONS

Six months after receipt of the second dose of the BNT162b2 vaccine, humoral response was substantially decreased, especially among men, among persons 65 years of age or older, and among persons with immunosuppression.

Published in NEJM (Oct. 6, 2021):

https://doi.org/10.1056/NEJMoa2114583 

BACKGROUND

Despite the high efficacy of the BNT162b2 messenger RNA vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), rare breakthrough infections have been reported, including infections among health care workers. Data are needed to characterize these infections and define correlates of breakthrough and infectivity.

METHODS

At the largest medical center in Israel, we identified breakthrough infections by performing extensive evaluations of health care workers who were symptomatic (including mild symptoms) or had known infection exposure. These evaluations included epidemiologic investigations, repeat reverse-transcriptase–polymerase-chain-reaction (RT-PCR) assays, antigen-detecting rapid diagnostic testing (Ag-RDT), serologic assays, and genomic sequencing. Correlates of breakthrough infection were assessed in a case–control analysis. We matched patients with breakthrough infection who had antibody titers obtained within a week before SARS-CoV-2 detection (peri-infection period) with four to five uninfected controls and used generalized estimating equations to predict the geometric mean titers among cases and controls and the ratio between the titers in the two groups. We also assessed the correlation between neutralizing antibody titers and N gene cycle threshold (Ct) values with respect to infectivity.

RESULTS

Among 1497 fully vaccinated health care workers for whom RT-PCR data were available, 39 SARS-CoV-2 breakthrough infections were documented. Neutralizing antibody titers in case patients during the peri-infection period were lower than those in matched uninfected controls (case-to-control ratio, 0.361; 95% confidence interval, 0.165 to 0.787). Higher peri-infection neutralizing antibody titers were associated with lower infectivity (higher Ct values). Most breakthrough cases were mild or asymptomatic, although 19% had persistent symptoms (>6 weeks). The B.1.1.7 (alpha) variant was found in 85% of samples tested. A total of 74% of case patients had a high viral load (Ct value, <30) at some point during their infection; however, of these patients, only 17 (59%) had a positive result on concurrent Ag-RDT. No secondary infections were documented.

CONCLUSIONS

Among fully vaccinated health care workers, the occurrence of breakthrough infections with SARS-CoV-2 was correlated with neutralizing antibody titers during the peri-infection period. Most breakthrough infections were mild or asymptomatic, although persistent symptoms did occur.

Published in NEJM (July 28, 2021):

https://doi.org/10.1056/NEJMoa2109072 

The short-term effectiveness of a two-dose regimen of the BioNTech/Pfizer mRNA BNT162b2 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine was widely demonstrated. However, long term effectiveness is still unknown. A nationwide vaccination campaign was initiated early in Israel, allowing for a real-world evaluation of the interaction between protection and time-from-vaccine. The Delta (B.1.617.2) variant became the dominant strain in Israel in June 2021, as Israel is currently experiencing a new surge of cases. Leveraging the centralized computerized database of Maccabi Healthcare Services (MHS), we assessed the correlation between time-from-vaccine and incidence of breakthrough infection. We found that the risk for infection was significantly higher for early vaccinees compared to those vaccinated later. This preliminary finding should prompt further investigagions into long-term protection against different strains, and prospective clinical trials to examine the effect of a booster vaccine against breakthrough infection.

Available as preprint in medRxiv (July 31, 2021):

https://doi.org/10.1101/2021.07.29.21261317 

The coronavirus variant discovered in South Africa can "break through" Pfizer/BioNTech's COVID-19 vaccine to some extent, a real-world data study in Israel found, though its prevalence in the country is low and the research has not been peer reviewed.  The study, released on Saturday, compared almost 400 people who had tested positive for COVID-19, 14 days or more after they received one or two doses of the vaccine, against the same number of unvaccinated patients with the disease. It matched age and gender, among other characteristics. The South African variant, B.1.351, was found to make up about 1% of all the COVID-19 cases across all the people studied, according to the study by Tel Aviv University and Israel’s largest healthcare provider, Clalit. But among patients who had received two doses of the vaccine, the variant’s prevalence rate was eight times higher than those unvaccinated - 5.4% versus 0.7%.  This suggests the vaccine is less effective against the South African variant, compared with the original coronavirus and a variant first identified in Britain that has come to comprise nearly all COVID-19 cases in Israel, the researchers said. “We found a disproportionately higher rate of the South African variant among people vaccinated with a second dose, compared to the unvaccinated group. This means that the South African variant is able, to some extent, to break through the vaccine’s protection,” said Tel Aviv University’s Adi Stern.

The researchers cautioned, though, that the study only had a small sample size of people infected with the South African variant because of its rarity in Israel. They also said the research was not intended to deduce overall vaccine effectiveness against any variant, since it only looked at people who had already tested positive for COVID-19, not at overall infection rates. Pfizer and BioNTech could not be immediately reached for comment outside business hours. The companies said on April 1 that their vaccine was around 91% effective at preventing COVID-19, citing updated trial data that included participants inoculated for up to six months. In respect to the South African variant, they said that among a group of 800 study volunteers in South Africa, where B.1.351 is widespread, there were nine cases of COVID-19, all of which occurred among participants who got the placebo. Of those nine cases, six were among individuals infected with the South African variant.

Some previous studies have indicated that the Pfizer/BioNTech shot was less potent against the B.1.351 variant than against other variants of the coronavirus, but still offered a robust defence.

While the results of the study may cause concern, the low prevalence of the South African strain was encouraging, according to Stern. “Even if the South African variant does break through the vaccine’s protection, it has not spread widely through the population,” said Stern, adding that the British variant may be “blocking” the spread of the South African strain. Almost 53% of Israel’s 9.3 million population has received both Pfizer doses. Israel has largely reopened its economy in recent weeks while the pandemic appears to be receding, with infection rates, severe illness and hospitalizations dropping sharply. About a third of Israelis are below the age of 16, which means they are still not eligible for the shot.

Findings available in medRxiv (April 9, 2021):

https://doi.org/10.1101/2021.04.06.21254882 

The researchers said the findings support policies delaying the second shot in efforts to stretch supplies and speed up immunizations. 

Nachman Ash reportedly says it's not certain vaccines can protect against mutated coronavirus strains; 12,400 Israelis were infected with virus after receiving 1st shot.  Israel’s coronavirus czar Nachman Ash has reportedly said the first dose of Pfizer’s vaccine provides less protection against COVID-19 than the US pharmaceutical firm had initially indicated it would, and cautioned that it may not protect against new strains of the virus. During talks among Health Ministry officials ahead of Tuesday’s cabinet meeting on the possibility of extending the nationwide lockdown, Ash questioned the effectiveness of the vaccine after just one dose, Army Radio reported Tuesday afternoon. Many people have gotten infected between the first and second Pfizer shots, Ash was quoted saying, and it appears that the protection offered by the first dose is “less effective than we had thought.” The data on the protective effect against the virus of the first dose is “lower than Pfizer presented,” he was quoted saying. According to the Health Ministry, over 12,400 have people tested positive for coronavirus after receiving vaccine shots; this figure includes 69 people who have received the second dose.

Pfizer says its vaccine, produced with BioNTech, is around 52% effective after the first dose, and increases to about 95% a number of days after the second dose. Last week, Sharon Alroy-Preis, head of the Health Ministry’s public health department, announced that the vaccine curbs infections by some 50 percent 14 days after the first of the two shots is administered. She said that the data was preliminary, and based on the results of coronavirus tests among both those who have received the vaccine and those who haven’t, who are are serving as a de facto control group.  At the same time, however, other, somewhat contrary data was released by Israeli health maintenance organizations: According to figures released by Clalit, Israel’s largest health provider, the chance of a person being infected with the coronavirus dropped by 33% 14 days after they were vaccinated; separate figures recorded by the Maccabi health provider showed the vaccine caused a 60% drop in the chances for infection after taking the first shot. During his talks with health officials on Tuesday, Ash also said that it was not certain the vaccine can protect against mutated variants of the coronavirus, according to the report. A month into Israel’s vaccination campaign, Health Ministry officials had hoped to see a drop in daily infections and serious cases, but there is no such trend at this time. The more contagious virus variants — particularly the British strain — are being blamed for the difficulty in bringing down illness rates and easing the heavy load on hospitals, despite the lockdown and mass vaccinations.

Speaking to ministers at Tuesday’s meeting of the so-called coronavirus cabinet, Ash said that health officials estimate the British coronavirus variant is behind 30%-40% of current infections and will become the dominant strain in Israel within weeks, according to Hebrew media reports. The mutated strain of the virus is more infectious, though it is not considered more deadly. Ash reportedly recommended extending the nationwide lockdown by two weeks until February 4, saying that the basic reproduction number, a key indicator of the virus’ transmission, was dropping but it would take another few days for the full effect of the lockdown to be felt. The Health Ministry said Tuesday morning that a record 10,021 infections were confirmed the previous day, bringing the country’s total caseload since the start of the pandemic to 562,167, including 81,059 active cases. The rate of positive tests passed the 10 percent mark for the first time in over three months, with 10.2% of the nearly 100,000 tests coming back positive.

A new study from Israel and the U.S. found the risk of infection was 2.37-fold higher between 90 and 119 days after completing the vaccine series compared to the initial 90 days.

• A new study looked at more than 80,000 adults who were fully vaccinated with the Pfizer-BioNTech vaccine
• The percentage of tests that came back positive increased from 1.3% prior to 90 days to of 2.4% 90 to 119 days later, to 10.3% 150 to 179 days later 
• Risk of infection was 2.37-fold higher between 90 and 119 days after completing the vaccine series compared to the initial 90 days
• This increased to a 2.82-fold increased risk 180 days or more after receiving the second dose
• Researchers say the findings show booster shots are likely needed to sustain long-term protection from Covid

Immunity against infection from COVID-19 vaccines is waning over time, a new study suggests. Researchers from the Leumit Health Services in Israel and the U.S. National Institutes of Health (NIH) looked at people inoculated with the Pfizer-BioNTech vaccine. They found that, 90 days after receiving the second dose, the risk of contracting the virus more than doubles and only keeps increasing as far as six months out.  What's more, the percentage of tests coming back positive for COVID-19 quadrupled from 2.4 percent at least 90 days later to 10.6 percent at least 150 days later. The finding add more evidence that, while the Pfizer vaccines provides strong protection in the initial weeks, booster shots are likely needed to sustain long-term protection from Covid.   Israel was one of the first countries to roll out use of Pfizer's Covid vaccine in December 2020 and the U.S. was not far behind. The Middle Eastern country experienced a resurgence in cases in September while infections are creeping up now in the U.S. This has led many experts to fear that immunity from the standard two-dose regimen wanes over time.  Researchers say determining the risk of infection as more time elapses since dose two can lead to important information about the optimal timing of a third dose.  

For the study, published in The BMJ, the team looked at the electronic health records of 80,057 adults in Israel. All of the adults were fully vaccinated with the Pfizer shot and had no history of a prior COVID-19 infection.  Of this group, 7,973 - or 9.6 percent - ended up testing positive for COVID-19. After matching patients to controls that were of the same age and racial/ethnic background, researchers found the rate of positive Covid tests increased the more time had passed since the second dose. Between 21 and 89 days after the second dose, only 1.3 percent of tests came back positive. However, between 90 and 119 days later, this rate nearly doubled to 2.4 percent, and only continued to grow. A total of 4.6 percent of tests came back positive 120 to 149 days after the second dose, increasing to 10.3 percent 150 to 179 days later and to 18.5 percent 180 days or more later.  Next, researchers looked at the risk of infection across all age groups compared to 90 days after the second dose. They found that the risk of infection with 2.37-fold higher between 90 and 119 days after completing the vaccine series. This only continued to increase to  2.66-fold higher after 120 to 149 days; 2.82-fold higher after 150 to 179 days; and 2.82-fold higher after 180 days or beyond.

Cited study Published in BMJ (Nov. 25, 2021):

 https://doi.org/10.1136/bmj-2021-067873 

BACKGROUND

Reports have suggested an association between the development of myocarditis and the receipt of messenger RNA (mRNA) vaccines against coronavirus disease 2019 (Covid-19), but the frequency and severity of myocarditis after vaccination have not been extensively explored.

METHODS

We searched the database of Clalit Health Services, the largest health care organization (HCO) in Israel, for diagnoses of myocarditis in patients who had received at least one dose of the BNT162b2 mRNA vaccine (Pfizer–BioNTech). The diagnosis of myocarditis was adjudicated by cardiologists using the case definition used by the Centers for Disease Control and Prevention. We abstracted the presentation, clinical course, and outcome from the patient’s electronic health record. We performed a Kaplan–Meier analysis of the incidence of myocarditis up to 42 days after the first vaccine dose.

RESULTS

Among more than 2.5 million vaccinated HCO members who were 16 years of age or older, 54 cases met the criteria for myocarditis. The estimated incidence per 100,000 persons who had received at least one dose of vaccine was 2.13 cases (95% confidence interval [CI], 1.56 to 2.70). The highest incidence of myocarditis (10.69 cases per 100,000 persons; 95% CI, 6.93 to 14.46) was reported in male patients between the ages of 16 and 29 years. A total of 76% of cases of myocarditis were described as mild and 22% as intermediate; 1 case was associated with cardiogenic shock. After a median follow-up of 83 days after the onset of myocarditis, 1 patient had been readmitted to the hospital, and 1 had died of an unknown cause after discharge. Of 14 patients who had left ventricular dysfunction on echocardiography during admission, 10 still had such dysfunction at the time of hospital discharge. Of these patients, 5 underwent subsequent testing that revealed normal heart function.

CONCLUSIONS

Among patients in a large Israeli health care system who had received at least one dose of the BNT162b2 mRNA vaccine, the estimated incidence of myocarditis was 2.13 cases per 100,000 persons; the highest incidence was among male patients between the ages of 16 and 29 years. Most cases of myocarditis were mild or moderate in severity. (Funded by the Ivan and Francesca Berkowitz Family Living Laboratory Collaboration at Harvard Medical School and Clalit Research Institute.)

Published in NEJM (Oct. 6, 2021):

https://doi.org/10.1056/NEJMoa2110737 

BACKGROUND

Preapproval trials showed that messenger RNA (mRNA)–based vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) had a good safety profile, yet these trials were subject to size and patient-mix limitations. An evaluation of the safety of the BNT162b2 mRNA vaccine with respect to a broad range of potential adverse events is needed.

METHODS

We used data from the largest health care organization in Israel to evaluate the safety of the BNT162b2 mRNA vaccine. For each potential adverse event, in a population of persons with no previous diagnosis of that event, we individually matched vaccinated persons to unvaccinated persons according to sociodemographic and clinical variables. Risk ratios and risk differences at 42 days after vaccination were derived with the use of the Kaplan–Meier estimator. To place these results in context, we performed a similar analysis involving SARS-CoV-2–infected persons matched to uninfected persons. The same adverse events were studied in the vaccination and SARS-CoV-2 infection analyses.

RESULTS

In the vaccination analysis, the vaccinated and control groups each included a mean of 884,828 persons. Vaccination was most strongly associated with an elevated risk of myocarditis (risk ratio, 3.24; 95% confidence interval [CI], 1.55 to 12.44; risk difference, 2.7 events per 100,000 persons; 95% CI, 1.0 to 4.6), lymphadenopathy (risk ratio, 2.43; 95% CI, 2.05 to 2.78; risk difference, 78.4 events per 100,000 persons; 95% CI, 64.1 to 89.3), appendicitis (risk ratio, 1.40; 95% CI, 1.02 to 2.01; risk difference, 5.0 events per 100,000 persons; 95% CI, 0.3 to 9.9), and herpes zoster infection (risk ratio, 1.43; 95% CI, 1.20 to 1.73; risk difference, 15.8 events per 100,000 persons; 95% CI, 8.2 to 24.2). SARS-CoV-2 infection was associated with a substantially increased risk of myocarditis (risk ratio, 18.28; 95% CI, 3.95 to 25.12; risk difference, 11.0 events per 100,000 persons; 95% CI, 5.6 to 15.8) and of additional serious adverse events, including pericarditis, arrhythmia, deep-vein thrombosis, pulmonary embolism, myocardial infarction, intracranial hemorrhage, and thrombocytopenia.

CONCLUSIONS

In this study in a nationwide mass vaccination setting, the BNT162b2 vaccine was not associated with an elevated risk of most of the adverse events examined. The vaccine was associated with an excess risk of myocarditis (1 to 5 events per 100,000 persons). The risk of this potentially serious adverse event and of many other serious adverse events was substantially increased after SARS-CoV-2 infection. (Funded by the Ivan and Francesca Berkowitz Family Living Laboratory Collaboration at Harvard Medical School and Clalit Research Institute.)

Published in New England J. Medicine (August 25, 2021):

https://doi.org/10.1056/NEJMoa2110475

Israel's Prime Minister has announced a program to roll out a third dose of the coronavirus vaccine to people over the age of 60, becoming one of the first countries in the world to make such a move.  People over 60 will need to show they received their second dose of the vaccine at least five months ago. Thursday's announcement follows a strong recommendation from the government-appointed team of experts on the pandemic to offer older adults a third dose. The experts' advice, which came overnight on Wednesday, was based on data suggesting significant waning immunity from infection over time. Some of the data considered by the health ministry comes from research on the "justification, safety and efficacy" of a third dose of the Pfizer-BioNTech vaccine for hemodialysis patients that was posted as a pre-print paper earlier this month.  The research found that about two-thirds of hemodialysis patients (people who require the procedure to remove waste products and excess fluid from the blood when the kidneys stop working properly) who had a suboptimal immune response after a second dose of the vaccine developed "optimal" antibodies and T cells after a third dose. From Tuesday to Thursday, the number of new cases in Israel has topped two thousand each day -- levels that have not been seen in the country for four and half months. Back in May and June, the number of new daily cases was down to single figures on some days.

Vaccinating many people against SARS-CoV-2 could stall infection rates even among unvaccinated children in the same community. Last December, Israel launched one of the fastest vaccination schemes in the world, reaching 50% of the population in 9 weeks. But only people aged 16 and over were eligible for the jab.

To test the ripple effects of widespread vaccination, Tal Patalon at Maccabi Healthcare Services in Tel Aviv-Yafo, Israel, Roy Kishony at the Technion — Israel Institute of Technology in Haifa and their colleagues analysed COVID-19 vaccinations and test results recorded between January and March 2021 for people in 223 Israeli communities (O. Milman et al. Preprint at medRxiv https://doi.org/f4d7; 2021). In each community, the authors examined the relationship between the vaccination rate in adults over three 3-week intervals and the rate of positive results for a COVID-19 test in children 35 days later. The authors found that, in the weeks after older people had received the Pfizer–BioNTech vaccine, the infection risk among children under 16 dropped proportionally to the percentage of adults who had been vaccinated. The authors warn that their results might be influenced by children who had previously been infected, even though the study included communities with low infection rates. The findings have not yet been peer reviewed.

Preprint available in medRxiv (March 31, 2021):

https://doi.org/10.1101/2021.03.26.21254394 

Maccabi health fund releases preliminary results of a study comparing vaccinated and not vaccinated members’ likability to contract the disease and said vaccine 92% effective.  A total of 371 out of 715,425 Israelis who passed at least a week after receiving two doses of the Pfizer coronavirus vaccine have contracted the virus – 0.04%, with 16 being sent to the hospital – according to a Health Ministry report released on Thursday. Immunity to COVID-19 is supposed to kick in a week after receiving the second dose of the Pfizer vaccine. According to the studies conducted by Pfizer, the vaccine had an efficacy of about 95%, which is considered very high. The Israeli data appear to confirm the inoculation’s effectiveness, showing an even more promising result. Later in the day, Maccabi Healthcare Services – one of the country’s four health maintenance organizations – released the first results of the vaccination campaign of its members, with the organization also comparing the data to a control group that did not get inoculated.