Real-World Effectiveness of COVID-19 Vaccine and Identification of SARS-CoV-2 Variants among People Living with HIV on Highly Active Antiretroviral Therapy in Central Kerala of India-An Ambi-Directional Cohort Study.

BACKGROUND: Vaccine effectiveness for first-generation coronavirus disease (COVID-19) vaccines among People Living with HIV (PLHIV) in India remains unexplored. This study entails the estimation of the real-world effectiveness of COVID-19 vaccines (AZD1222/Covishield, BBV152/Covaxin) among PLHIV and the identification of variants of SARS-CoV-2 among those infected with COVID-19. METHODS: An ambi-directional cohort study was conducted among 925 PLHIV above 18 years of age in two districts of central Kerala, India, from February 2022 to March 2023. Selected PLHIV were recruited as Participant Liaison Officers (PLOs) for the follow-up on the study participants. At enrolment, basic details, baseline CD4 count, and a Nasopharyngeal (NP) swab for RT-PCR were collected. In the follow-up phase, NP swabs were collected from subjects with COVID-19 symptoms. Positive subjects had a CD4 count and genomic sequencing performed. RESULTS: The mean age of the participants was 46.93 ± 11.00 years. The majority, 819 (93.6%), of participants had received at least one dose of any vaccine, while 56 (6.4%) were unvaccinated. A total of 649 (79.24%) participants were vaccinated with Covishield and 169 (20.63%) with Covaxin. In the vaccinated group, 158 (19.3%) reported COVID-19 infection. Vaccine Effectiveness (VE) for one dose of any vaccine was 43.2% (95% CI: 11.8-64.5), p = 0.015. The effectiveness of full vaccination with Covishied was 63.8% (95% CI: 39.3-79.2), p < 0.001, and Covaxin was 73.4% (95% CI: 44.3-87.3). VE was highest, at 60.7% (95% CI: 23.6-81.3), when the two doses of the vaccine were given at an interval of less than 6 weeks. Participants with a baseline CD4 count > 350 had greater protection from COVID-19, at 53.4% (95% CI: 19.6-75.3) p = 0.004. The incident cases were sub-variants of Omicron (BA.2, BA.2.38, BA.2.10). CONCLUSIONS: Full vaccination with Covishield and Covaxin was effective against COVID-19 infection among PLHIV on treatment; albeit, that of Covaxin was higher. A gap of 4 to 6 weeks between the two doses of COVID-19 vaccine was found to have higher VE among PLHIV.

Active Symptom-Based Surveillance of Adverse Events Following Immunization Among Individuals Vaccinated with ChAdOx1 nCoV-19 Coronavirus Vaccine in a Tertiary Hospital of Kerala.

BACKGROUND: The reports on adverse experiences following vaccination are scanty from India. It is important to know the real-world post-vaccination experience outside of clinical trial conditions. OBJECTIVES: The study aims to estimate the incidence of adverse events following immunization with the ChAdOx1 nCoV-19 coronavirus vaccine and to identify the predictors for the development of vaccine adverse events. METHODS: A prospective observational study was conducted among health care workers who received the ChAdOx1 nCoV-19 coronavirus vaccine. Study participants were monitored at the site for 30 min following vaccination and were followed up for 7 days after receiving the second dose, with a purpose-specific designed online surveillance form to enquire about any adverse events following vaccination. We used the Chi-squared test for categorical variables and multivariate regression analysis to identify predictors for the development of vaccine adverse effects. RESULTS: Of 411 participants, the mean age was 30.77 ± 12.5 years and 76.2% were females. Overall, 207 (50.4%) respondents reported at least one post-vaccination symptom receiving either dose of coronavirus vaccination. Fever (34.8%), local pain at the injection site (28.0%), tiredness (25.5%), chills (20%), myalgia (18.7%), headache (17.8%), injection site stiffness (5.4%), joint pain (4.6%) and nausea-vomiting (3.8%) were the most prevalent symptoms following the first dose. Adverse reactions reported after the second dose were milder and less frequent. Postvaccination symptoms were more likely in the younger age group, those with comorbidity particularly, bronchial asthma , and a history of allergy to food/drugs. CONCLUSION: All the adverse reactions were of a minor type and non-serious. Side effects were less common in older adults (>60 years). Reactions to the second dose were lesser in intensity and frequency. Younger age, history of allergy, and comorbidities, particularly asthma, were found to be major predictors for the development of adverse events and require more watchful vaccine administration.

Linear canonical transform as a tool to analyze coherence properties of electromagnetic beams propagating in a quadratic phase system.

Linear canonical transformation (LCT) provides a generalized and elegant mathematical framework for analyzing the coherence properties of an electromagnetic (EM) beam propagating in quadratic phase systems (QPSs). It is shown that LCT may be used to analyze coherence properties such as generalized Stokes parameters and EM degree of coherence of a partially coherent EM beam propagating through a QPS. We present simulation results of a Gaussian Schell model beam propagating through a Fourier system, fractional Fourier system, and 4f imaging system with an aperture and beam relay system.

Statistical investigation of the double random phase encoding technique.

The amplitude-encoding case of the double random phase encoding technique is examined by defining a cost function as a metric to compare an attempted decryption against the corresponding original input image. For the case when a cipher-text pair has been obtained and the correct decryption key is unknown, an iterative attack technique can be employed to ascertain the key. During such an attack the noise in the output field for an attempted decryption can be used as a measure of a possible decryption key's correctness. For relatively small systems, i.e., systems involving fewer than 5x5 pixels, the output decryption of every possible key can be examined to evaluate the distribution of the keys in key space in relation to their relative performance when carrying out decryption. However, in order to do this for large systems, checking every single key is currently impractical. One metric used to quantify the correctness of a decryption key is the normalized root mean squared (NRMS) error. The NRMS is a measure of the cumulative intensity difference between the input and decrypted images. We identify a core term in the NRMS, which we refer to as the difference parameter, d. Expressions for the expected value (or mean) and variance of d are derived in terms of the mean and variance of the output field noise, which is shown to be circular Gaussian. These expressions assume a large sample set (number of pixels and keys). We show that as we increase the number of samples used, the decryption error obeys the statistically predicted characteristic values. Finally, we corroborate previously reported simulations in the literature by using the statistically derived expressions.

Compact portable ocular microtremor sensor: design, development and calibration.

Ocular microtremor (OMT) is a physiological high-frequency (up to 150 Hz) low-amplitude (25-2500 nm peak-to-peak) involuntary motion of the human eye. Recent studies suggest a number of clinical applications for OMT that include monitoring the depth of anesthesia of a patient in surgery, prediction of outcome in coma, and diagnosis of brain stem death. Clinical OMT investigations to date have used mechanical piezoelectric probes or piezoelectric strain gauges that have many drawbacks which arise from the fact that the probe is in contact with the eye. We describe the design of a compact noncontact sensing device to measure OMT that addresses some of the above drawbacks. We evaluate the system performance using a calibrated piezoelectric vibrator that simulates OMT signals under conditions that can occur in practice, i.e., wet eye conditions. We also test the device at low light levels well within the eye safety range.

Coherence effects in digital in-line holographic microscopy.

We analyze the effects of partial coherence in the image formation of a digital in-line holographic microscope (DIHM). The impulse response is described as a function of cross-spectral density of the light used in the space-frequency domain. Numerical simulation based on the applied model shows that a reduction in coherence of light leads to broadening of the impulse response. This is also validated by results from experiments wherein a DIHM is used to image latex beads using light with different spatial and temporal coherence.

Role of phase key in the double random phase encoding technique: an error analysis.

We perform a numerical analysis of the double random phase encryption-decryption technique to determine how, in the case of both amplitude and phase encoding, the two decryption keys (the image- and Fourier-plane keys) affect the output gray-scale image when they are in error. We perform perfect encryption and imperfect decryption. We introduce errors into the decrypting keys that correspond to the use of random distributions of incorrect pixel values. We quantify the effects that increasing amounts of error in the image-plane key, the Fourier-plane key, and both keys simultaneously have on the decrypted image. Quantization effects are also examined.

Generalized in-line digital holographic technique based on intensity measurements at two different planes.

In-line digital holography based on two-intensity measurements [Zhang Opt. Lett. 29, 1787 (2004)], is modified by introducing a pi shifting in the reference phase. Such an improvement avoids the assumption that the object beam must be much weaker than the reference beam in strength and results in a simplified experimental implementation. Computer simulations and optical experiments are carried out to validate the method, which we refer to as position-phase-shifting digital holography.

Noninterferometric phase retrieval using a fractional Fourier system.

The signal extraction method based on intensity measurements in two close fractional Fourier domains is examined by using the phase space formalism. The fractional order separation has a lower bound and an upper bound that depend on the signal at hand and the noise in the optical system used for measurement. On the basis of a theoretical analysis, it is shown that for a given optical system a judicious choice of fractional order separation requires some a priori knowledge of the signal bandwidth. We also present some experimental results in support of the analysis.

Controlling speckle using lenses and free space.

The correlation properties of speckle fields are studied for general paraxial systems. The previous studies on lateral and longitudinal speckle size for the case of free-space propagation (Fresnel transform) are generalized to the case of the linear canonical transform. These results have implications for the control of speckle size, through appropriate design of optical systems, with particular relevance for speckle interferometry.

Key-space analysis of double random phase encryption technique.

We perform a numerical analysis on the double random phase encryption/decryption technique. The key-space of an encryption technique is the set of possible keys that can be used to encode data using that technique. In the case of a strong encryption scheme, many keys must be tried in any brute-force attack on that technique. Traditionally, designers of optical image encryption systems demonstrate only how a small number of arbitrary keys cannot decrypt a chosen encrypted image in their system. However, this type of demonstration does not discuss the properties of the key-space nor refute the feasibility of an efficient brute-force attack. To clarify these issues we present a key-space analysis of the technique. For a range of problem instances we plot the distribution of decryption errors in the key-space indicating the lack of feasibility of a simple brute-force attack.

Cryptanalysis of optical security systems with significant output images.

The security of the encryption and verification techniques with significant output images is examined by a known-plaintext attack. We introduce an iterative phase-retrieval algorithm based on multiple intensity measurements to heuristically estimate the phase key in the Fourier domain by several plaintext-cyphertext pairs. We obtain correlation output images with very low error by correlating the estimated key with corresponding random phase masks. Our studies show that the convergence behavior of this algorithm sensitively depends on the starting point. We also demonstrate that this algorithm can be used to attack the double random phase encoding technique.

Generalized Yamaguchi correlation factor for coherent quadratic phase speckle metrology systems with an aperture.

In speckle-based metrology systems, a finite range of possible motion or deformation can be measured. When coherent imaging systems with a single limiting aperture are used in speckle metrology, the observed decorrelation effects that ultimately define this range are described by the well-known Yamaguchi correlation factor. We extend this result to all coherent quadratic phase paraxial optical systems with a single aperture and provide experimental results to support our theoretical conclusions.

Paraxial speckle-based metrology systems with an aperture.

Digital speckle photography can be used in the analysis of surface motion in combination with an optical linear canonical transform (LCT). Previously [D. P. Kelly et al. Appl. Opt.44, 2720 (2005)] it has been shown that optical fractional Fourier transforms (OFRTs) can be used to vary the range and sensitivity of speckle-based metrology systems, allowing the measurement of both the magnitude and direction of tilting (rotation) and translation motion simultaneously, provided that the motion is captured in two separate OFRT domains. This requires two bulk optical systems. We extend the OFRT analysis to more general LCT systems with a single limiting aperture. The effect of a limiting aperture in LCT systems is examined in more detail by deriving a generalized Yamaguchi correlation factor. We demonstrate the benefits of using an LCT approach to metrology design. Using this technique, we show that by varying the curvature of the illuminating field, we can effectively change the output domain. From a practical perspective this means that estimation of the motion of a target can be achieved by using one bulk optical system and different illuminating conditions. Experimental results are provided to support our theoretical analysis.

Polarization encoding and multiplexing of two-dimensional signals: application to image encryption.

We discuss an optical system that encodes an input signal to a polarization state, using a spatial light modulator (SLM). Using two SLMs the optical system multiplexes two 2D signals in the polarization domain, and we demonstrate the multiplexing of two binary images. The encryption and decryption of two binary images using an XOR operation is also presented.

Intranasal exposure to staphylococcal enterotoxin B elicits an acute systemic inflammatory response.

Staphylococcus aureus produces a variety of superantigen exotoxins, including staphylococcal enterotoxin B (SEB). Little is known regarding the pathogenesis of SEB entering through the intranasal route. Intranasal exposure to SEB might occur because of nasal packing following surgical procedure, biologic warfare, or even S. aureus colonization. We evaluated the local and systemic effects of intranasally delivered SEB using a series of human leukocyte antigen (HLA) class II transgenic mice as conventional mice expressing endogenous class II molecules mount a poor immune response to SEB. Gene expression profiling using microarrays showed robust up-regulation of genes involved in several proinflammatory pathways as early as 3 h post-intranasal challenge with SEB in HLA class II transgenic mice. This was accompanied by a several hundred-fold increase in serum levels of pro-inflammatory cytokines such as IL-12, IL-6, TNF-alpha, IFN-gamma, as well as MCP-1 in HLA class II transgenic mice but not in C57BL/6 mice; CD4 or CD8 T-cells independently contributed to the systemic cytokine response. Defective IL-12 or IL-4 receptor signaling significantly decreased or increased serum IFN-gamma, respectively. Intranasal exposure to SEB resulted in neutrophil influx into bronchoalveolar lavage fluid and caused expansion of both CD4 and CD8 T-cells expressing TCR V beta 8 in the spleen. This was accompanied by mononuclear cell infiltration in the liver reminiscent of the systemic inflammatory response syndrome. Thus, we have shown, for the first time, that intranasal administration of SEB can cause systemic immune activation.

A known-plaintext heuristic attack on the Fourier plane encryption algorithm.

The Fourier plane encryption algorithm is subjected to a known-plaintext attack. The simulated annealing heuristic algorithm is used to estimate the key, using a known plaintext-ciphertext pair, which decrypts the ciphertext with arbitrarily low error. The strength of the algorithm is tested by using this estimated key to decrypt a different ciphertext which was also encrypted using the same original key. We assume that the plaintext is amplitude-encoded real-valued image, and analyze only the mathematical algorithm rather than a real optical system that can be more secure. The Fourier plane encryption algorithm is found to be susceptible to a known-plaintext heuristic attack.

Lensless sensor system using a reference structure.

We describe a reference structure based sensor system for tracking the motion of an object. The reference structure is designed to implement a Hadamard transformation over a range of angular perspectives. We implemented a reference structure with an angular resolution of 5(o) and a field of view of 40(o).